v3.26.3
Investment Risks
Sep. 28, 2026
LARGE CAP FUND | SIIT LARGE CAP FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
LARGE CAP FUND | SIIT LARGE CAP FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
LARGE CAP FUND | SIIT LARGE CAP FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

LARGE CAP FUND | SIIT LARGE CAP FUND | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

LARGE CAP FUND | SIIT LARGE CAP FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole.

LARGE CAP FUND | SIIT LARGE CAP FUND | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

LARGE CAP FUND | SIIT LARGE CAP FUND | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

LARGE CAP FUND | SIIT LARGE CAP FUND | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

LARGE CAP FUND | SIIT LARGE CAP FUND | Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments.

LARGE CAP FUND | SIIT LARGE CAP FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment

in the Fund would be adversely affected. Currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

LARGE CAP FUND | SIIT LARGE CAP FUND | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

LARGE CAP FUND | SIIT LARGE CAP FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts is subject to leverage risk, correlation risk, liquidity risk and market risk. Leverage risk and liquidity risk are described below and market risk is described above. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

LARGE CAP FUND | SIIT LARGE CAP FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

LARGE CAP FUND | SIIT LARGE CAP FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole. Sub-Adviser(s) may exhibit poor security selection, losing money on both the long and short sides.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s investments in securities denominated in foreign currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Short Sales Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Short Sales Risk — A short sale involves the sale of a security that the Fund does not own in the expectation of purchasing the same security (or a security exchangeable therefore) at a later date at a lower price. Short sales expose the Fund to the risk that it will be required to buy the security sold short (also known as “covering” the short position) at a time when the security has appreciated in value, thus resulting in a loss to the Fund. Investment in short sales may also cause the Fund to incur expenses related to borrowing securities. Reinvesting proceeds received from short selling may create leverage, which can amplify the effects of market volatility on the Fund’s share price. In addition, shorting a future contract may require posting only a margin that may amount to less than the notional exposure of the contract. Such a practice may exacerbate the loss in a case of adverse price action.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts and swaps is subject to leverage risk, correlation risk, liquidity risk and market risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

LARGE CAP DISCIPLINED EQUITY FUND | SIIT LARGE CAP DISCIPLINED EQUITY FUND | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Risk Nondiversified Status [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Non-Diversification Risk — In seeking to track the Index, the Fund may become non-diversified as a result of a change in relative market capitalization or index weighting of one or more constituents of the Index. A non-diversified fund generally invests a greater portion of its assets in the securities of one or more issuers and invests overall in a smaller number of issuers than a diversified fund. When it is non-diversified, the Fund may be more sensitive to a single economic, business, political, regulatory, or other occurrences, which may negatively impact the Fund’s performance and result in greater fluctuation in the value of the Fund’s shares.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that its investment approach, which attempts to replicate the performance of the Russell 1000 Index, may underperform other segments of the equity markets or the equity markets as a whole. The Fund is also subject to the risk that large capitalization securities may underperform other segments of the equity markets or the equity markets as a whole.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Tracking Error Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Tracking Error Risk — The risk that the Fund’s performance may vary substantially from the performance of the benchmark index it tracks as a result of cash flows, Fund expenses, imperfect correlation between the Fund’s investments and the index’s components and other factors.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Sampling Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Sampling Risk — The Fund may not fully replicate the benchmark index and may hold securities not included in the index. As a result, the Fund may not track the return of its benchmark index as well as it would have if the Fund purchased all of the securities in its benchmark index.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as ADRs, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities,

including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

LARGE CAP INDEX FUND | SIIT LARGE CAP INDEX FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Risk Nondiversified Status [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Non-Diversification Risk — In seeking to track the Index, the Fund may become non-diversified as a result of a change in relative market capitalization or index weighting of one or more constituents of the Index. A non-diversified fund generally invests a greater portion of its assets in the securities of one or more issuers and invests overall in a smaller number of issuers than a diversified fund. When it is non-diversified, the Fund may be more sensitive to a single economic, business, political, regulatory, or other occurrences, which may negatively impact the Fund’s performance and result in greater fluctuation in the value of the Fund’s shares.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that the Fund’s investment approach, which attempts to replicate the performance of the S&P 500 Index, may underperform other segments of the equity markets or the equity markets as a whole.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Tracking Error Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Tracking Error Risk — The risk that the Fund’s performance may vary substantially from the performance of the benchmark index it tracks as a result of cash flows, Fund expenses, imperfect correlation between the Fund’s and benchmark’s investments and other factors.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as ADRs, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies

will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — Smaller capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts is subject to leverage risk, correlation risk, liquidity risk and market risk. Leverage risk and liquidity risk are described below and market risk is described above. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. Each of these risks could cause the Fund to lose more than the principal

amount invested in a derivative instrument. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

S&P 500 INDEX FUND | SIIT S&P 500 Index Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Risk Nondiversified Status [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Non-Diversification Risk — In seeking to track the Index, the Fund may become non-diversified as a result of a change in relative market capitalization or index weighting of one or more constituents of the Index. A non-diversified fund generally invests a greater portion of its assets in the securities of one or more issuers and invests overall in a smaller number of issuers than a diversified fund. When it is non-diversified, the Fund may be more sensitive to a single economic, business, political, regulatory, or other occurrences, which may negatively impact the Fund’s performance and result in greater fluctuation in the value of the Fund’s shares.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that the Fund’s investment approach, which attempts to replicate the performance of the Index, may underperform other segments of the equity markets or the equity markets as a whole. The Fund is also subject to the risk that the securities in which it invests may underperform other segments of the equity markets or the equity markets as a whole.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Tracking Error Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Tracking Error Risk — The risk that the Fund’s performance may vary substantially from the performance of the Index as a result of cash flows, Fund expenses, imperfect correlation between the Fund’s investments and the benchmark and other factors.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Sampling Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Sampling Risk — The Fund may not fully replicate the Index and may hold securities not included in the Index. As a result, the Fund may not track the return of the Index as well as it would have if the Fund purchased all of the securities in the Index.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small and medium capitalization stocks may be more volatile than those of larger companies. Small and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forwards contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many OTC derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts, options and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Repurchase Agreements and Reverse Repurchase Agreements Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Repurchase Agreements and Reverse Repurchase Agreements Risk — In the event of the insolvency of the counterparty to a repurchase agreement or reverse repurchase agreement, recovery of the repurchase price owed to the Fund or, in the case of a reverse repurchase agreement, the securities sold by the Fund, may be delayed. Because reverse repurchase agreements may be considered to be the practical equivalent of borrowing funds, they constitute a form of leverage. If the Fund reinvests the proceeds of a reverse

repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Fund’s yield.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Money Market Funds [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Money Market Funds — An investment in a money market fund is not a bank deposit and is not insured or guaranteed by any bank, the Federal Deposit Insurance Corporation (FDIC) or any other government agency. Certain money market funds float their NAV while others seek to preserve the value of investments at a stable NAV (typically, $1.00 per share). An investment in a money market fund, even an investment in a fund seeking to maintain a stable NAV per share, is not guaranteed and it is possible for the Fund to lose money by investing in these and other types of money market funds. If the liquidity of a money market fund’s portfolio deteriorates below certain levels, the money market fund may suspend redemptions (i.e., impose a redemption gate) and thereby prevent the Fund from selling its investment in the money market fund or impose a fee of up to 2% on amounts the Fund redeems from the money market fund (i.e., impose a liquidity fee). Money market funds and the securities they invest in are subject to comprehensive regulations. The enactment of new legislation or regulations, as well as changes in interpretation and enforcement of current laws, may affect the manner of operation, performance and/or yield of money market funds.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives and repurchase agreements (which effectively constitute a form of borrowing) may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments.

EXTENDED MARKET INDEX FUND | SIIT Extended Market Index Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

SMALL CAP FUND | SIIT SMALL CAP FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
SMALL CAP FUND | SIIT SMALL CAP FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
SMALL CAP FUND | SIIT SMALL CAP FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

SMALL CAP FUND | SIIT SMALL CAP FUND | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

SMALL CAP FUND | SIIT SMALL CAP FUND | Quantitative Investing Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Quantitative Investing Risk — A quantitative investment style generally involves the use of computers to implement a systematic or rules-based approach to selecting investments based on specific measurable factors. Due to the significant role technology plays in such strategies, they carry the risk of unintended or unrecognized issues or flaws in the design, coding, implementation or maintenance of the computer programs or technology used in the development and implementation of the quantitative strategy.

SMALL CAP FUND | SIIT SMALL CAP FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that small capitalization securities may underperform other segments of the equity markets or the equity markets as a whole.

SMALL CAP FUND | SIIT SMALL CAP FUND | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

SMALL CAP FUND | SIIT SMALL CAP FUND | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

SMALL CAP FUND | SIIT SMALL CAP FUND | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

SMALL CAP FUND | SIIT SMALL CAP FUND | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small and medium capitalization stocks may be more volatile than those of larger companies. Small and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

SMALL CAP FUND | SIIT SMALL CAP FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

SMALL CAP FUND | SIIT SMALL CAP FUND | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

SMALL CAP II FUND | SIIT Small Cap II Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
SMALL CAP II FUND | SIIT Small Cap II Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
SMALL CAP II FUND | SIIT Small Cap II Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

SMALL CAP II FUND | SIIT Small Cap II Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

SMALL CAP II FUND | SIIT Small Cap II Fund | Quantitative Investing Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Quantitative Investing Risk — A quantitative investment style generally involves the use of computers to implement a systematic or rules-based approach to selecting investments based on specific measurable factors. Due to the significant role technology plays in such strategies, they carry the risk of unintended or unrecognized issues or flaws in the design, coding, implementation or maintenance of the computer programs or technology used in the development and implementation of the quantitative strategy.

SMALL CAP II FUND | SIIT Small Cap II Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that the securities in which the Fund principally invests may underperform other segments of the equity markets or the equity markets as a whole.

SMALL CAP II FUND | SIIT Small Cap II Fund | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

SMALL CAP II FUND | SIIT Small Cap II Fund | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

SMALL CAP II FUND | SIIT Small Cap II Fund | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of

underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

SMALL CAP II FUND | SIIT Small Cap II Fund | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small and medium capitalization stocks may be more volatile than those of larger companies. Small and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

SMALL CAP II FUND | SIIT Small Cap II Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

SMALL CAP II FUND | SIIT Small Cap II Fund | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments.

SMALL CAP II FUND | SIIT Small Cap II Fund | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that smaller and medium capitalization securities may underperform other segments of the equity market or the equity markets as a whole.

SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general

or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

SMALL/MID CAP EQUITY FUND | SIIT SMALL MID CAP EQUITY FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Quantitative Investing Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Quantitative Investing Risk — A quantitative investment style generally involves the use of computers to implement a systematic or rules-based approach to selecting investments based on specific measurable factors. Due to the significant role technology plays in such strategies, they carry the risk of unintended or unrecognized issues or flaws in the design, coding, implementation or maintenance of the computer programs or technology used in the development and implementation of the quantitative strategy.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that the Fund’s investment strategy may underperform other segments of the equity markets or the equity markets as a whole.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as ADRs, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Convertible and Preferred Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Convertible and Preferred Securities Risk — Convertible and preferred securities have many of the same characteristics as stocks, including many of the same risks. In addition, convertible securities may be more

sensitive to changes in interest rates than stocks. Convertible securities may also have credit ratings below investment grade, meaning that they carry a higher risk of failure by the issuer to pay principal and/or interest when due.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Structured Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Structured Securities Risk — The payment and credit qualities of structured securities derive from their underlying assets, and they may behave in ways not anticipated by the Fund, or they may not receive tax, accounting or regulatory treatment anticipated by the Fund.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — Small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small and medium capitalization stocks may be more volatile than those of larger companies. Small and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that equity securities of U.S. companies of all capitalization ranges may underperform other segments of the equity markets or the equity markets as a whole.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | American Depositary Receipts (ADRs) Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

American Depositary Receipts (ADRs) Risk — ADRs are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. ADRs are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory and tax environments.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

U.S. MANAGED VOLATILITY FUND | SIIT U.S. Managed Volatility Fund | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Small and Medium Capitalization Companies Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Companies Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that securities selected as part of a managed volatility strategy may underperform other segments of the equity markets or the equity markets as a whole.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts and forward contracts is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many OTC derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly

with the underlying asset, rate or index. The Fund’s use of forward contracts is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

GLOBAL MANAGED VOLATILITY FUND | SIIT Global Managed Volatility Fund | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that equity securities of developed and emerging market countries may underperform other segments of the equity markets or the equity markets as a whole.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in

economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forwards contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many OTC derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts, options and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Long/Short Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Long/Short Risk — The Fund seeks long exposure to certain financial instruments and short exposure to certain other financial instruments. There is no guarantee that the returns on the Fund’s long or short positions will produce positive returns and the Fund could lose money if either or both the Fund’s long and short positions produce negative returns.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

WORLD EQUITY EX-US FUND | SIIT WORLD EQUITY EX-US FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that equity securities of developed and emerging market countries may underperform other segments of the equity markets or the equity markets as a whole.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Social Investment Criteria Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Social Investment Criteria Risk — The Fund’s portfolio is subject to certain social investment criteria, including its anti-BDS approach. As a result, the Sub-Advisers will avoid purchasing certain securities for social reasons when it is otherwise economically advantageous to purchase those securities or may sell certain securities for social reasons when it is otherwise economically advantageous to hold those securities. In general, the application of the Fund’s social investment criteria may affect the Fund’s exposure to certain industries, sectors and geographic areas, which may affect the financial performance of the Fund, positively or negatively, depending on whether these industries or sectors are in or out of favor.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forwards contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many OTC derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts, options and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain

derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Long/Short Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Long/Short Risk — The Fund seeks long exposure to certain financial instruments and short exposure to certain other financial instruments. There is no guarantee that the returns on the Fund’s long or short positions will produce positive returns and the Fund could lose money if either or both the Fund’s long and short positions produce negative returns.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

SCREENED WORLD EQUITY EX-US FUND | SIIT Screened World Equity Ex-US Fund | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity or bond market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Foreign Investment/Emerging and Frontier Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging and Frontier Markets Risk — The risk that non-U.S. securities may be subject to additional price volatility, illiquidity and decreases in value due to, among other things, political, social and economic developments abroad, government ownership or control of portions of the private sector or certain companies, trade barriers and currency movements, exchange controls and managed adjustments in relative currency values, and different or new and unsettled securities and tax markets, laws and regulations. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. These risks may be magnified further with respect to “frontier market countries,” which are a subset of emerging market countries with even smaller national economies. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about

emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Country Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Country Concentration Risk — The Fund’s concentration of its assets in issuers located in a single country or a limited number of countries will increase the impact of, and potential losses associated with, the risks set forth in the Foreign Investment/Emerging and Frontier Markets Risk.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Risk of Investing in China [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Risk of Investing in China — Because China is an emerging market that may be subject to considerable government intervention and varying degrees of economic, political and social instability, such investments may be subject to greater risk of stock market, interest rate, and currency fluctuations, as well as inflation.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — The risk that larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that emerging market equity securities may underperform other segments of the equity markets or the equity markets as a whole.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Participation Notes (P-Notes) Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Participation Notes (P-Notes) Risk — P-Notes are participation interest notes that are issued by banks or broker-dealers and are designed to offer a return linked to a particular underlying equity, debt, currency or market. Investments in P-Notes involve the same risks associated with a direct investment in the underlying foreign companies or foreign securities markets that they seek to replicate. However, there can be no assurance that the trading price of P-Notes will equal the underlying value of the foreign companies or foreign securities markets that they seek to replicate.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The risk that small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small and medium capitalization companies may have limited product lines, markets and financial resources, and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forwards contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many OTC derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts, options and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Commodity-Linked Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commodity-Linked Securities Risk — Investments in commodity-linked securities may be more volatile and less liquid than direct investments in the underlying commodities themselves. Commodity-related equity returns can also be affected by the issuer’s financial structure or the performance of unrelated businesses.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Investment Company Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company Risk — When the Fund invests in an investment company, including closed-end funds and ETFs, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the investment company’s expenses. Further, while the risks of owning shares of an investment company generally reflect the risks of owning the underlying investments of the investment company, the Fund may be subject to additional or different risks than if the Fund had invested directly in the underlying investments. For example, the lack of liquidity in an ETF could result in its value being more volatile than that of the underlying portfolio securities. Closed-end investment companies issue a fixed number of shares that trade on a stock exchange or over-the-counter at a premium or a discount to their net asset value. As a result, a closed-end fund’s share price fluctuates based on what another investor is willing to pay rather than on the market value of the securities in the fund.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments.

EMERGING MARKETS EQUITY FUND | SIIT EMERGING MARKETS EQUITY FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value

if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that short-duration fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Below Investment Grade Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Below Investment Grade Securities Risk — Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are generally more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Bank Loans Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Bank Loans Risk — With respect to bank loans, the Fund will assume the credit risk of both the borrower of the loan and the lender that is selling the participation in the loan. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Commercial Paper Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commercial Paper Risk — Commercial paper is a short-term obligation with a maturity generally ranging from one to 270 days and is issued by U.S. or foreign companies or other entities in order to finance their current operations. Such investments are unsecured and usually discounted from their value at maturity. The value of commercial paper may be affected by changes in the credit rating or financial condition of the issuing entities and will tend to fall when interest rates rise and rise when interest rates fall. Asset-backed commercial paper may be issued by structured investment vehicles or other conduits that are organized to issue the commercial paper and to purchase trade receivables or other financial assets. The repayment of asset-backed commercial paper depends primarily on the cash collections received from such an issuer’s underlying asset portfolio and the issuer’s ability to issue new asset-backed commercial paper.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Investing in Limited Recourse Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investing in Limited Recourse Obligations Risk — Collateralized debt obligation (CDO) and collateralized loan obligation (CLO) securities are non-recourse obligations of their issuer payable solely from the related underlying collateral or its proceeds. Therefore, as a holder of CDOs and CLOs, the Fund must rely only on distributions on the underlying collateral or related proceeds for payment. If distributions on the underlying collateral are insufficient to make payments on the CDO or CLO securities, no other assets will be available for payment of the deficiency. As a result, the amount and timing of interest and principal payments in respect of CDO and CLO securities will depend on the performance and characteristics of the related underlying collateral.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forwards contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts, options and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Repurchase Agreements and Reverse Repurchase Agreements Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Repurchase Agreements and Reverse Repurchase Agreements Risk — In the event of the insolvency of the counterparty to a repurchase agreement or reverse repurchase agreement, recovery of the repurchase price owed to the Fund or, in the case of a reverse repurchase agreement, the securities sold by the Fund, may be delayed. Because reverse repurchase agreements may be considered to be the practical equivalent of borrowing funds, they constitute a form of leverage. If the Fund reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Fund’s yield.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Asset-Backed Securities Risk — Payment of principal and interest on asset-backed securities is dependent largely on the cash flows generated by the assets backing the securities. Securitization trusts generally do not have any assets or sources of funds other than receivables and related property they own, and asset-backed securities are generally not insured or guaranteed by the related sponsor or any other entity. Asset-backed securities may be more illiquid than more conventional types of fixed income securities that the Fund may acquire.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage-Backed Securities Risk — Mortgage-backed securities are affected significantly by the rate of prepayments and modifications of the mortgage loans backing those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-backed securities are particularly sensitive to prepayment risk, which is described below, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities; however, the timing and amount of prepayments cannot be accurately predicted. The timing of changes in the rate of prepayments of the mortgage loans may significantly affect the Fund’s actual yield to maturity on any mortgage-backed securities, even if the average rate of principal payments is consistent with the Fund’s expectation. Along with prepayment risk, mortgage-backed securities are significantly affected by interest rate risk, which is described above. In a low interest rate environment, mortgage loan prepayments would

generally be expected to increase due to factors such as refinancings and loan modifications at lower interest rates. In contrast, if prevailing interest rates rise, prepayments of mortgage loans would generally be expected to decline and therefore extend the weighted average lives of mortgage-backed securities held or acquired by the Fund.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Mortgage Dollar Rolls Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage Dollar Rolls Risk — Mortgage dollar rolls are transactions in which the Fund sells securities (usually mortgage-backed securities) and simultaneously contracts to repurchase substantially similar, but not identical, securities on a specified future date. If the broker-dealer to whom the Fund sells the security becomes insolvent, the Fund’s right to repurchase the security may be restricted. Other risks involved in entering into mortgage dollar rolls include the risk that the value of the security may change adversely over the term of the mortgage dollar roll and that the security the Fund is required to repurchase may be worth less than the security that the Fund originally held.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives and repurchase agreements (which effectively constitute a form of borrowing) may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

OPPORTUNISTIC INCOME FUND | SIIT Opportunistic Income Fund | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other

developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that the fixed income securities in which the Fund invests may underperform other segments of the fixed income markets or the fixed income markets as a whole.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Below Investment Grade Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Below Investment Grade Securities Risk — Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are generally more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Bank Loans Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Bank Loans Risk — With respect to bank loans, the Fund will assume the credit risk of both the borrower and the lender that is selling the participation. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates,

intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forwards contracts and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Asset-Backed Securities Risk — Payment of principal and interest on asset-backed securities is dependent largely on the cash flows generated by the assets backing the securities. Securitization trusts generally do not have any assets or sources of funds other than receivables and related property they own, and asset-backed

securities are generally not insured or guaranteed by the related sponsor or any other entity. Asset-backed securities may be more illiquid than more conventional types of fixed income securities that the Fund may acquire.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage-Backed Securities Risk — Mortgage-backed securities are affected significantly by the rate of prepayments and modifications of the mortgage loans backing those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-backed securities are particularly sensitive to prepayment risk, which is described below, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities; however, the timing and amount of prepayments cannot be accurately predicted. The timing of changes in the rate of prepayments of the mortgage loans may significantly affect the Fund’s actual yield to maturity on any mortgage-backed securities, even if the average rate of principal payments is consistent with the Fund’s expectation. Along with prepayment risk, mortgage-backed securities are significantly affected by interest rate risk, which is described above. In a low interest rate environment, mortgage loan prepayments would generally be expected to increase due to factors such as refinancings and loan modifications at lower interest rates. In contrast, if prevailing interest rates rise, prepayments of mortgage loans would generally be expected to decline and therefore extend the weighted average lives of mortgage-backed securities held or acquired by the Fund.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Mortgage Dollar Rolls Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage Dollar Rolls Risk — Mortgage dollar rolls are transactions in which the Fund sells securities (usually mortgage-backed securities) and simultaneously contracts to repurchase substantially similar, but not identical, securities on a specified future date. If the broker-dealer to whom the Fund sells the security becomes insolvent, the Fund’s right to repurchase the security may be restricted. Other risks involved in entering into mortgage dollar rolls include the risk that the value of the security may change adversely over the term of the mortgage dollar roll and that the security the Fund is required to repurchase may be worth less than the security that the Fund originally held.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

CORE FIXED INCOME FUND | SIIT CORE FIXED INCOME | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Below Investment Grade Securities (Junk Bonds) Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Below Investment Grade Securities (Junk Bonds) Risk — Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are generally more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is

speculative. Because these securities typically offer a higher rate of return to compensate investors for these risks, they are sometimes referred to as “high yield bonds,” but there is no guarantee that an investment in these securities will result in a high rate of return.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that high yield fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Bank Loans Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Bank Loans Risk — With respect to bank loans, the Fund will assume the credit risk of both the borrower of the loan and the lender that is selling the participation in the loan. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Investing in Limited Recourse Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investing in Limited Recourse Obligations Risk — Collateralized debt obligation (CDO) and collateralized loan obligation (CLO) securities are non-recourse obligations of their issuer payable solely from the related underlying collateral or its proceeds. Therefore, as a holder of CDOs and CLOs, the Fund must rely only on distributions on the underlying collateral or related proceeds for payment. If distributions on the underlying collateral are insufficient to make payments on the CDO or CLO securities, no other assets will be available for payment of the deficiency. As a result, the amount and timing of interest and principal payments in respect of CDO and CLO securities will depend on the performance and characteristics of the related underlying collateral.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Convertible and Preferred Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Convertible and Preferred Securities Risk — Convertible and preferred securities have many of the same characteristics as stocks, including many of the same risks. In addition, convertible bonds may be more sensitive to changes in interest rates than stocks. Convertible bonds may also have credit ratings below investment grade, meaning that they carry a higher risk of failure by the issuer to pay principal and/or interest when due.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forwards contracts and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the

derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

HIGH YIELD BOND FUND | SIIT HIGH YIELD BOND FUND | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

LONG DURATION FUND | SIIT LONG DURATION FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
LONG DURATION FUND | SIIT LONG DURATION FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
LONG DURATION FUND | SIIT LONG DURATION FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events,

the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

LONG DURATION FUND | SIIT LONG DURATION FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that longer-term U.S. fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.

LONG DURATION FUND | SIIT LONG DURATION FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund.

LONG DURATION FUND | SIIT LONG DURATION FUND | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

LONG DURATION FUND | SIIT LONG DURATION FUND | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

LONG DURATION FUND | SIIT LONG DURATION FUND | Foreign Sovereign Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Sovereign Debt Securities Risk — The risks that (i) the governmental entity that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or interest when it becomes due, because of factors such as debt service burden, political constraints, cash flow problems and other national economic factors; (ii) governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments; and (iii) there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part.

LONG DURATION FUND | SIIT LONG DURATION FUND | Municipal Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Municipal Securities Risk — Municipal securities, like other fixed income securities, rise and fall in value in response to economic and market factors, primarily changes in interest rates, and actual or perceived credit

quality. Rising interest rates will generally cause municipal securities to decline in value. Longer-term securities respond more sharply to interest rate changes than do shorter-term securities. A municipal security will also lose value if, due to rating downgrades or other factors, there are concerns about the issuer’s current or future ability to make principal or interest payments. State and local governments rely on taxes and, to some extent, revenues from private projects financed by municipal securities, to pay interest and principal on municipal debt. Poor statewide or local economic results or changing political sentiments may reduce tax revenues and increase the expenses of municipal issuers, making it more difficult for them to repay principal and to make interest payments on securities owned by the Fund. Actual or perceived erosion of the creditworthiness of municipal issuers may reduce the value of the Fund’s holdings. As a result, the Fund will be more susceptible to factors that adversely affect issuers of municipal obligations than a mutual fund that does not have as great a concentration in municipal obligations.

LONG DURATION FUND | SIIT LONG DURATION FUND | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

LONG DURATION FUND | SIIT LONG DURATION FUND | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

LONG DURATION FUND | SIIT LONG DURATION FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

LONG DURATION FUND | SIIT LONG DURATION FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures, forwards and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

LONG DURATION FUND | SIIT LONG DURATION FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

LONG DURATION FUND | SIIT LONG DURATION FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

LONG DURATION FUND | SIIT LONG DURATION FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

LONG DURATION FUND | SIIT LONG DURATION FUND | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

LONG DURATION FUND | SIIT LONG DURATION FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

LONG DURATION FUND | SIIT LONG DURATION FUND | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

LONG DURATION FUND | SIIT LONG DURATION FUND | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events,

the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that longer duration corporate fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Foreign Sovereign Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Sovereign Debt Securities Risk — The risks that (i) the governmental entity that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or interest when it becomes due, because of factors such as debt service burden, political constraints, cash flow problems and other national economic factors; (ii) governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments; and (iii) there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Municipal Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Municipal Securities Risk — Municipal securities, like other fixed income securities, rise and fall in value in response to economic and market factors, primarily changes in interest rates, and actual or perceived credit quality. Rising interest rates will generally cause municipal securities to decline in value. Longer-term securities respond more sharply to interest rate changes than do shorter-term securities. A municipal security will also lose value if, due to rating downgrades or other factors, there are concerns about the issuer’s current or future ability to make principal or interest payments. State and local governments rely on taxes and, to some extent, revenues from private projects financed by municipal securities, to pay interest and principal on

municipal debt. Poor statewide or local economic results or changing political sentiments may reduce tax revenues and increase the expenses of municipal issuers, making it more difficult for them to repay principal and to make interest payments on securities owned by the Fund. Actual or perceived erosion of the creditworthiness of municipal issuers may reduce the value of the Fund’s holdings. As a result, the Fund will be more susceptible to factors that adversely affect issuers of municipal obligations than a mutual fund that does not have as great a concentration in municipal obligations.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s investments in securities denominated in foreign currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of options and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

LONG DURATION CREDIT FUND | SIIT Long Duration Credit Fund | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and additional capital gains tax liabilities, which may affect the Fund’s performance.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that short-duration fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Commercial Paper Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commercial Paper Risk — Commercial paper is a short-term obligation with a maturity generally ranging from one to 270 days and is issued by U.S. or foreign companies or other entities in order to finance their current operations. Such investments are unsecured and usually discounted from their value at maturity. The value of commercial paper may be affected by changes in the credit rating or financial condition of the issuing entities and will tend to fall when interest rates rise and rise when interest rates fall. Asset-backed commercial paper may be issued by structured investment vehicles or other conduits that are organized to issue the commercial paper and to purchase trade receivables or other financial assets. The repayment of asset-backed commercial paper depends primarily on the cash collections received from such an issuer’s underlying asset portfolio and the issuer’s ability to issue new asset-backed commercial paper.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Investing in Limited Recourse Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investing in Limited Recourse Obligations Risk — Collateralized debt obligation (CDO) and collateralized loan obligation (CLO) securities are non-recourse obligations of their issuer payable solely from the related underlying collateral or its proceeds. Therefore, as a holder of CDOs and CLOs, the Fund must rely only on distributions on the underlying collateral or related proceeds for payment. If distributions on the underlying collateral are insufficient to make payments on the CDO or CLO securities, no other assets will be available

for payment of the deficiency. As a result, the amount and timing of interest and principal payments in respect of CDO and CLO securities will depend on the performance and characteristics of the related underlying collateral.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s investments in securities denominated in foreign currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, options, interest rate swaps and credit default swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts, credit-linked notes and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Investment Company Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company Risk — When the Fund invests in an investment company, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the investment company’s expenses. In addition, while the risks of owning shares of an investment company generally reflect the risks of owning the underlying investments of the investment company, the Fund may be subject to additional or different risks than if the Fund had invested directly in the underlying investments. For example, the lack of liquidity in an exchange-traded fund could result in its value being more volatile than the underlying portfolio securities.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Repurchase Agreements and Reverse Repurchase Agreements Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Repurchase Agreements and Reverse Repurchase Agreements Risk — In the event of the insolvency of the counterparty to a repurchase agreement or reverse repurchase agreement, recovery of the repurchase price owed to the Fund or, in the case of a reverse repurchase agreement, the securities sold by the Fund, may be delayed. Because reverse repurchase agreements may be considered to be the practical equivalent of borrowing funds, they constitute a form of leverage. If the Fund reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Fund’s yield.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Asset-Backed Securities Risk — Payment of principal and interest on asset-backed securities is dependent largely on the cash flows generated by the assets backing the securities. Securitization trusts generally do not have any assets or sources of funds other than receivables and related property they own, and asset-backed securities are generally not insured or guaranteed by the related sponsor or any other entity. Asset-backed securities may be more illiquid than more conventional types of fixed income securities that the Fund may acquire.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage-Backed Securities Risk — Mortgage-backed securities are affected significantly by the rate of prepayments and modifications of the mortgage loans backing those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-backed securities are particularly sensitive to prepayment risk, which is described below, given that the term to

maturity for mortgage loans is generally substantially longer than the expected lives of those securities; however, the timing and amount of prepayments cannot be accurately predicted. The timing of changes in the rate of prepayments of the mortgage loans may significantly affect the Fund’s actual yield to maturity on any mortgage-backed securities, even if the average rate of principal payments is consistent with the Fund’s expectation. Along with prepayment risk, mortgage-backed securities are significantly affected by interest rate risk, which is described above. In a low interest rate environment, mortgage loan prepayments would generally be expected to increase due to factors such as refinancings and loan modifications at lower interest rates. In contrast, if prevailing interest rates rise, prepayments of mortgage loans would generally be expected to decline and therefore extend the weighted average lives of mortgage-backed securities held or acquired by the Fund.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives and repurchase agreements (which effectively constitute a form of borrowing) may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest tend to be more volatile than shorter-term securities. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

ULTRA SHORT DURATION BOND FUND | SIIT Ultra Short Duration Bond Fund | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Risk Nondiversified Status [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Non-Diversified Risk — The Fund is non-diversified, which means that it may invest in the securities of relatively few issuers. As a result, the Fund may be more susceptible to a single adverse economic or political occurrence affecting one or more of these issuers and may experience increased volatility due to its investments in those securities. However, the Fund intends to satisfy the asset diversification requirements under Subchapter M of the Internal Revenue Code of 1986, as amended, for classification as a regulated investment company.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Below Investment Grade Securities (Junk Bonds) Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Below Investment Grade Securities (Junk Bonds) Risk — Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are generally more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. Because these securities typically offer a higher rate of return to compensate investors for these risks, they are sometimes referred to as “high yield bonds,” but there is no guarantee that an investment in these securities will result in a high rate of return.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that emerging market debt securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Foreign Sovereign Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Sovereign Debt Securities Risk — The risks that (i) the governmental entity that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or interest when it becomes due, because of factors such as debt service burden, political constraints, cash flow problems and other national economic factors; (ii) governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments; and (iii) there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Exchange-Traded Funds Risk — The risks of owning shares of an ETF generally reflect the risks of owning the underlying securities the ETF is designed to track, although lack of liquidity in an ETF could result in its value being more volatile than the underlying portfolio securities. When the Fund invests in an ETF, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s expenses.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies and the Fund’s active management of its currency exposures, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forward contracts, swaps and credit-linked notes is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of forward contracts, credit-linked notes and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Market risk is described above. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

EMERGING MARKETS DEBT FUND | SIIT EMERGING MARKETS DEBT FUND | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and additional capital gains tax liabilities, which may affect the Fund’s performance.

REAL RETURN FUND | SIIT Real Return Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
REAL RETURN FUND | SIIT Real Return Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
REAL RETURN FUND | SIIT Real Return Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

REAL RETURN FUND | SIIT Real Return Fund | Inflation Protected Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Inflation Protected Securities Risk — The value of inflation protected securities, including TIPS, generally will fluctuate in response to changes in “real” interest rates, generally decreasing when real interest rates rise and increasing when real interest rates fall. Real interest rates represent nominal (or stated) interest rates reduced by the expected impact of inflation. In addition, interest payments on inflation-indexed securities will generally vary up or down along with the rate of inflation.

REAL RETURN FUND | SIIT Real Return Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The Fund is also subject to the risk that the Fund’s securities may underperform other segments of the markets or the markets as a whole.

REAL RETURN FUND | SIIT Real Return Fund | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

REAL RETURN FUND | SIIT Real Return Fund | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

REAL RETURN FUND | SIIT Real Return Fund | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

REAL RETURN FUND | SIIT Real Return Fund | Commercial Paper Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commercial Paper Risk — Commercial paper is a short-term obligation with a maturity generally ranging from one to 270 days and is issued by U.S. or foreign companies or other entities in order to finance their current operations. Such investments are unsecured and usually discounted from their value at maturity. The value of commercial paper may be affected by changes in the credit rating or financial condition of the issuing entities and will tend to fall when interest rates rise and rise when interest rates fall. Asset-backed commercial paper may be issued by structured investment vehicles or other conduits that are organized to issue the commercial paper and to purchase trade receivables or other financial assets. The repayment of asset-backed commercial paper depends primarily on the cash collections received from such an issuer’s underlying asset portfolio and the issuer’s ability to issue new asset-backed commercial paper.

REAL RETURN FUND | SIIT Real Return Fund | Foreign Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments.

REAL RETURN FUND | SIIT Real Return Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected.

REAL RETURN FUND | SIIT Real Return Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts is subject to market risk, leverage risk, correlation risk and liquidity risk. Market risk and liquidity risk are described above, and leverage risk is described below. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

REAL RETURN FUND | SIIT Real Return Fund | Repurchase Agreements and Reverse Repurchase Agreements Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Repurchase Agreements and Reverse Repurchase Agreements Risk — In the event of the insolvency of the counterparty to a repurchase agreement or reverse repurchase agreement, recovery of the repurchase price owed to the Fund or, in the case of a reverse repurchase agreement, the securities sold by the Fund, may be delayed. Because reverse repurchase agreements may be considered to be the practical equivalent of borrowing funds, they constitute a form of leverage. If the Fund reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Fund’s yield.

REAL RETURN FUND | SIIT Real Return Fund | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage-Backed Securities Risk — Mortgage-backed securities are affected significantly by the rate of prepayments and modifications of the mortgage loans backing those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-backed securities are particularly sensitive to prepayment risk, which is described below, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities; however, the timing and amount of prepayments cannot be accurately predicted. The timing of changes in the rate of prepayments of the mortgage loans may significantly affect the Fund’s actual yield to maturity on any mortgage-backed securities, even if the average rate of principal payments is consistent with the Fund’s expectation. Along with prepayment risk, mortgage-backed securities are significantly affected by interest rate risk, which is described above. In a low interest rate environment, mortgage loan prepayments would generally be expected to increase due to factors such as refinancings and loan modifications at lower interest rates. In contrast, if prevailing interest rates rise, prepayments of mortgage loans would generally be expected to decline and therefore extend the weighted average lives of mortgage-backed securities held or acquired by the Fund.

REAL RETURN FUND | SIIT Real Return Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

REAL RETURN FUND | SIIT Real Return Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

REAL RETURN FUND | SIIT Real Return Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

REAL RETURN FUND | SIIT Real Return Fund | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

REAL RETURN FUND | SIIT Real Return Fund | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

REAL RETURN FUND | SIIT Real Return Fund | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Risk Money Market Fund Price Fluctuates [Member]  
Prospectus [Line Items]  
Risk [Text Block] In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.
LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Risk Money Market Fund May Not Preserve Dollar [Member]  
Prospectus [Line Items]  
Risk [Text Block] This could have a significant adverse effect on the Fund’s ability to maintain a stable $1.00 share price, and, in extreme circumstances, could cause the Fund to suspend redemptions and liquidate completely.
LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Risk Money Market Fund Sponsor May Not Provide Support [Member]  
Prospectus [Line Items]  
Risk [Text Block] Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.
LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Bank Loans Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Bank Loans Risk — With respect to bank loans, the Fund will assume the credit risk of both the borrower and the lender that is selling the participation. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Investing in Limited Recourse Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investing in Limited Recourse Obligations Risk — Collateralized debt obligation (CDO) and collateralized loan obligation (CLO) securities are non-recourse obligations of their issuer payable solely from the related underlying collateral or its proceeds. Therefore, as a holder of CDOs and CLOs, the Fund must rely only on distributions on the underlying collateral or related proceeds for payment. If distributions on the underlying collateral are insufficient to make payments on the CDO or CLO securities, no other assets will be available for payment of the deficiency. As a result, the amount and timing of interest and principal payments in respect of CDO and CLO securities will depend on the performance and characteristics of the related underlying collateral.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, forwards contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below, and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of OTC forwards, options and swaps is also subject to credit risk and valuation risk. Credit risk is described above. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Asset-Backed Securities Risk — Payment of principal and interest on asset-backed securities is dependent largely on the cash flows generated by the assets backing the securities. Securitization trusts generally do not have any assets or sources of funds other than receivables and related property they own, and asset-backed securities are generally not insured or guaranteed by the related sponsor or any other entity. Asset-backed securities may be more illiquid than more conventional types of fixed income securities that the Fund may acquire.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage-Backed Securities Risk — Mortgage-backed securities are affected significantly by the rate of prepayments and modifications of the mortgage loans backing those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-backed securities are particularly sensitive to prepayment risk, which is described below, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities; however, the timing and amount of prepayments cannot be accurately predicted. The timing of changes in the rate of prepayments of the mortgage loans may significantly affect the Fund’s actual yield to maturity on any mortgage-backed securities, even if the average rate of principal payments is consistent with the Fund’s expectation. Along with prepayment risk, mortgage-backed securities are significantly affected by interest rate risk, which is described above. In a low interest rate environment, mortgage loan prepayments would generally be expected to increase due to factors such as refinancings and loan modifications at lower interest rates. In contrast, if prevailing interest rates rise, prepayments of mortgage loans would generally be expected to decline and therefore extend the weighted average lives of mortgage-backed securities held or acquired by the Fund.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Mortgage Dollar Rolls Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage Dollar Rolls Risk — Mortgage dollar rolls are transactions in which the Fund sells securities (usually mortgage-backed securities) and simultaneously contracts to repurchase substantially similar, but not identical, securities on a specified future date. If the broker-dealer to whom the Fund sells the security becomes insolvent, the Fund’s right to repurchase the security may be restricted. Other risks involved in entering into mortgage dollar rolls include the risk that the value of the security may change adversely over the term of the mortgage dollar roll and that the security the Fund is required to repurchase may be worth less than the security that the Fund originally held.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Foreign Investment and Foreign Issuer Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment and Foreign Issuer Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory and tax environments.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Redemption Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Redemption Risk — The Fund may experience periods of heavy redemptions that could cause the Fund to liquidate its assets at inopportune times or at a loss or depressed value, particularly during periods of declining or illiquid markets. This could have a significant adverse effect on the Fund’s ability to maintain a stable $1.00 share price, and, in extreme circumstances, could cause the Fund to suspend redemptions and liquidate completely.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

LIMITED DURATION BOND FUND | SIIT Limited Duration Bond Fund | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Investment Style Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Style Risk — The risk that intermediate duration corporate fixed income securities may underperform other segments of the fixed income markets or the fixed income markets as a whole.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Foreign Sovereign Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Sovereign Debt Securities Risk — The risks that (i) the governmental entity that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or interest when it becomes due, because of factors such as debt service burden, political constraints, cash flow problems and other national economic factors; (ii) governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments; and (iii) there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Municipal Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Municipal Securities Risk — Municipal securities, like other fixed income securities, rise and fall in value in response to economic and market factors, primarily changes in interest rates, and actual or perceived credit quality. Rising interest rates will generally cause municipal securities to decline in value. Longer-term securities respond more sharply to interest rate changes than do shorter-term securities. A municipal security will also lose value if, due to rating downgrades or other factors, there are concerns about the issuer’s current or future ability to make principal or interest payments. State and local governments rely on taxes and, to some extent, revenues from private projects financed by municipal securities, to pay interest and principal on municipal debt. Poor statewide or local economic results or changing political sentiments may reduce tax revenues and increase the expenses of municipal issuers, making it more difficult for them to repay principal and to make interest payments on securities owned by the Fund. Actual or perceived erosion of the

creditworthiness of municipal issuers may reduce the value of the Fund’s holdings. As a result, the Fund will be more susceptible to factors that adversely affect issuers of municipal obligations than a mutual fund that does not have as great a concentration in municipal obligations.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures contracts, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below, and market risk is described above. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of options and swaps is also subject to credit risk and valuation risk. Credit risk is described above. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Investment Company Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company Risk — When the Fund invests in an investment company, including ETFs, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the investment company’s expenses. Further, while the risks of owning shares of an investment company generally reflect the risks of owning the underlying investments of the investment company, the Fund may be subject to additional or different risks than if the Fund had invested directly in the underlying investments. For example, the lack of liquidity in an ETF could result in its value being more volatile than that of the underlying portfolio securities.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest may be more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

INTERMEDIATE DURATION CREDIT FUND | SIIT Intermediate Duration Credit Fund | Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Portfolio Turnover Risk — Due to its investment strategy, the Fund may buy and sell securities frequently. This may result in higher transaction costs and taxes subject to ordinary income tax rates as opposed to more favorable capital gains rates, which may affect the Fund’s performance.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You could lose money on your investment in the Fund, just as you could with other investments.
DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Equity Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Equity Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the equity or bond market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Fixed Income Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Fixed Income Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response

to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — If valuations of large capitalization companies appear to be greatly out of proportion to the valuations of small or medium capitalization companies, investors may migrate to the stocks of small and medium sized companies. Additionally, larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Below Investment Grade Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Below Investment Grade Securities Risk — Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are generally more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. These risks may be increased in foreign and emerging markets.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory, tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Foreign Sovereign Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Sovereign Debt Securities Risk — The risks that (i) the governmental entity that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or interest when it becomes due, because of factors such as debt service burden, political constraints, cash flow problems and other national economic factors; (ii) governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments; and (iii) there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Bank Loans Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Bank Loans Risk — With respect to bank loans, the Fund will assume the credit risk of both the borrower and the lender that is selling the participation in the loan. The Fund may also have difficulty disposing of bank loans because, in certain cases, the market for such instruments is not highly liquid.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Commercial Paper Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commercial Paper Risk — Commercial paper is a short-term obligation with a maturity generally ranging from one to 270 days and is issued by U.S. or foreign companies or other entities in order to finance their current operations. Such investments are unsecured and usually discounted from their value at maturity. The value of commercial paper may be affected by changes in the credit rating or financial condition of the issuing entities and will tend to fall when interest rates rise and rise when interest rates fall. Asset-backed commercial paper may be issued by structured investment vehicles or other conduits that are organized to issue the commercial paper and to purchase trade receivables or other financial assets. The repayment of asset-backed commercial paper depends primarily on the cash collections received from such an issuer’s underlying asset portfolio and the issuer’s ability to issue new asset-backed commercial paper.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Investing in Limited Recourse Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investing in Limited Recourse Obligations Risk — Collateralized debt obligation (CDO) and collateralized loan obligation (CLO) securities are non-recourse obligations of their issuer payable solely from the related underlying collateral or its proceeds. Therefore, as a holder of CDOs and CLOs, the Fund must rely only on distributions on the underlying collateral or related proceeds for payment. If distributions on the underlying collateral are insufficient to make payments on the CDO or CLO securities, no other assets will be available for payment of the deficiency. As a result, the amount and timing of interest and principal payments in respect of CDO and CLO securities will depend on the performance and characteristics of the related underlying collateral.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Private Placements Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Private Placements Risk — Investment in privately placed securities may be less liquid than in publicly traded securities. Although these securities may be resold in privately negotiated transactions, the prices realized from these sales could be less than those originally paid by the Fund or less than what may be considered the fair value of such securities. Further, companies whose securities are not publicly traded may not be subject to the disclosure and other investor protection requirements that might be applicable if their securities were publicly traded.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Convertible and Preferred Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Convertible and Preferred Securities Risk — Convertible and preferred securities have many of the same characteristics as stocks, including many of the same risks. In addition, convertible bonds may be more sensitive to changes in interest rates than stocks. Convertible bonds may also have credit ratings below investment grade, meaning that they carry a higher risk of failure by the issuer to pay principal and/or interest when due.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Tax Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Tax Risk — The Fund may gain most of its exposure to the commodities markets through its investment in the Subsidiary, which invests in commodity investments and derivative instruments. The Fund’s investment in the Subsidiary is expected to provide the Fund with exposure to the commodities markets within the limitations of the federal tax requirements of Subchapter M of the Internal Revenue Code of 1986, as amended (the Code) for qualification as a regulated investment company (RIC). To the extent the Fund invests in such instruments directly, it will seek to restrict the resulting income from commodity-linked derivative instruments that do not generate qualifying income, such as commodity-linked swaps, to a maximum of 10% of its gross income (when combined with its other investments that produce non-qualifying income) to comply with the qualifying income test necessary for the Fund to qualify as a RIC under Subchapter M of the Code. However, the Fund may generate more non-qualifying income than anticipated, may not be able to generate qualifying income in a particular taxable year at levels sufficient to meet the qualifying income requirement, or may not be able to accurately predict the non-qualifying income from these investments. Accordingly, the extent to which the Fund invests in commodities or commodity-linked derivative instruments directly may be limited by the requirements of Subchapter M of the Code, which the Fund must continue to

satisfy to maintain its status as a RIC. Failure to comply with such requirements could have significant negative consequences to Fund shareholders. Under certain circumstances, the Fund may be able to cure a failure to meet the qualifying income requirement, but in order to do so the Fund may incur significant Fund‑level taxes, which would effectively reduce (and could eliminate) the Fund’s returns. See the “Taxes” section of the SAI for additional information.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that

the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Inflation Protected Securities [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Inflation Protected Securities — The value of investments in inflation protected securities, including TIPS, will generally fluctuate in response to changes in “real” interest rates. Real interest rates represent nominal interest rates reduced by the expected impact of inflation. The value of an inflation-protected security generally decreases when real interest rates rise and generally increases when real interest rates fall. In addition, the principal value of an inflation-protected security is periodically adjusted up or down along with the rate of inflation. If the measure of inflation falls, the principal value of the inflation-protected security will be adjusted downwards, and, consequently, the interest payable on the security will be reduced. Repayment of the original bond principal upon maturity (as adjusted for inflation) is guaranteed by the U.S. Treasury in the case of TIPS. For securities that do not provide a similar guarantee, the adjusted principal value of the security to be repaid at maturity is subject to credit risk.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs are subject to the risks associated with the direct ownership of real estate, which are discussed above. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Small Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small Capitalization Risk — Smaller capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, small capitalization companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization stocks may be more volatile than those of larger companies. Small capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Short Sales Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Short Sales Risk — A short sale involves the sale of a security that the Fund does not own in the expectation of purchasing the same security (or a security exchangeable therefore) at a later date at a lower price. Short sales expose the Fund to the risk that it will be required to buy the security sold short (also known as “covering” the short position) at a time when the security has appreciated in value, thus resulting in a loss to the Fund. Investment in short sales may also cause the Fund to incur expenses related to borrowing securities.

Reinvesting proceeds received from short selling may create leverage, which can amplify the effects of market volatility on the Fund’s share price. In addition, shorting a future contract may require posting only a margin that may amount to less than the notional exposure of the contract. Such a practice may exacerbate the loss in a case of adverse price action.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Real Estate Industry Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Real Estate Industry Risk — Securities of companies principally engaged in the real estate industry may be subject to the risks associated with direct ownership of real estate. Risks commonly associated with the direst ownership of real estate include fluctuations in the value of underlying properties, defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures, forwards, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Market risk and leverage risk are described above, and liquidity risk is described below. Many over-the-counter (OTC) derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of OTC forwards, options and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Commodity-Linked Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commodity-Linked Securities Risk — Investments in commodity-linked securities may be more volatile and less liquid than direct investments in the underlying commodities themselves. Commodity-related equity returns can also be affected by the issuer’s financial structure or the performance of unrelated businesses.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Investment Company Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company Risk — When the Fund invests in an investment company, including closed-end funds and ETFs, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the investment company’s expenses. Further, while the risks of owning shares of an investment company generally reflect the risks of owning the underlying investments of the investment company, the Fund may be subject to additional or different risks than if the Fund had invested directly in the underlying investments. For example, the lack of liquidity in an ETF could result in its value being more volatile than that of the underlying portfolio securities. Closed-end investment companies issue a fixed number of shares that trade on a stock exchange or over-the-counter at a premium or a discount to their net asset value. As a result, a closed-end fund’s share price fluctuates based on what another investor is willing to pay rather than on the market value of the securities in the fund.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Investment in the Subsidiary Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment in the Subsidiary Risk — The Subsidiary is not registered under the Investment Company Act of 1940, as amended (the 1940 Act), and, unless otherwise noted in this prospectus, is not subject to all of the investor protections of the 1940 Act. Thus, the Fund, as an investor in the Subsidiary, will not have all of the protections offered to investors in registered investment companies. In addition, changes in the laws of the United States and/or the Cayman Islands, under which the Fund and the Subsidiary, respectively, are organized, could result in the inability of the Fund and/or the Subsidiary to operate as intended and could negatively affect the Fund and its shareholders.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Commodity Investments and Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commodity Investments and Derivatives Risk — Commodity investments and derivatives may be more volatile and less liquid than direct investments in the underlying commodities themselves. Commodity-related equity returns can also be affected by the issuer’s financial structure or the performance of unrelated businesses. The value of a commodity investment or a derivative investment in commodities is typically based upon the price movements of a physical commodity, a commodity futures contract or commodity index or some other readily measurable economic variable that is dependent upon changes in the value of commodities or the commodities markets. The value of these securities will rise or fall in response to changes in the underlying commodity or related benchmark or investment, changes in interest rates or factors affecting a particular industry or commodity, such as natural disasters, weather and U.S. and international economic, political and regulatory developments.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Repurchase Agreements and Reverse Repurchase Agreements Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Repurchase Agreements and Reverse Repurchase Agreements Risk — In the event of the insolvency of the counterparty to a repurchase agreement or reverse repurchase agreement, recovery of the repurchase price owed to the Fund or, in the case of a reverse repurchase agreement, the securities sold by the Fund, may be delayed. Because reverse repurchase agreements may be considered to be the practical equivalent of borrowing funds, they constitute a form of leverage. If the Fund reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Fund’s yield.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Asset-Backed Securities Risk — Payment of principal and interest on asset-backed securities is dependent largely on the cash flows generated by the assets backing the securities. Securitization trusts generally do not have any assets or sources of funds other than receivables and related property they own, and asset-backed securities are generally not insured or guaranteed by the related sponsor or any other entity. Asset-backed securities may be more illiquid than more conventional types of fixed income securities that the Fund may acquire.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage-Backed Securities Risk — Mortgage-backed securities are affected significantly by the rate of prepayments and modifications of the mortgage loans backing those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-backed securities are particularly sensitive to prepayment risk, which is described below, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities; however, the timing and amount of prepayments cannot be accurately predicted. The timing of changes in the rate of prepayments of the mortgage loans may significantly affect the Fund’s actual yield to maturity on any mortgage-backed securities, even if the average rate of principal payments is consistent with the Fund’s expectation. Along with prepayment risk, mortgage-backed securities are significantly affected by interest rate risk, which is described above. In a low interest rate environment, mortgage loan prepayments would generally be expected to increase due to factors such as refinancings and loan modifications at lower interest rates. In contrast, if prevailing interest rates rise, prepayments of mortgage loans would generally be expected to decline and therefore extend the weighted average lives of mortgage-backed securities held or acquired by the Fund.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Mortgage Dollar Rolls Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage Dollar Rolls Risk — Mortgage dollar rolls are transactions in which the Fund sells securities (usually mortgage-backed securities) and simultaneously contracts to repurchase substantially similar, but not identical, securities on a specified future date. If the broker-dealer to whom the Fund sells the security becomes insolvent, the Fund’s right to repurchase the security may be restricted. Other risks involved in entering into mortgage dollar rolls include the risk that the value of the security may change adversely over the term of the mortgage dollar roll and that the security the Fund is required to repurchase may be worth less than the security that the Fund originally held.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives and repurchase agreements (which effectively constitute a form of borrowing) may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest tend to be more volatile than shorter-term securities. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

DYNAMIC ASSET ALLOCATION FUND | SIIT Dynamic Asset Allocation Fund | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, in a declining interest rate environment, fixed income securities with stated interest rates may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] In addition, the methodology by which SIMC allocates the Fund’s assets to the Sub-Adviser(s) may not achieve desired results and may cause the Fund to lose money or underperform other comparable mutual funds.
MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Equity Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Equity Market Risk — The risk that the market value of a security may move up and down, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an industry, a sector or the bond market as a whole. Equity markets may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Fixed Income Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Fixed Income Market Risk — The prices of the Fund’s fixed income securities respond to economic developments, particularly interest rate changes, as well as to perceptions about the creditworthiness of individual issuers, including governments and their agencies. Generally, the Fund’s fixed income securities will

decrease in value if interest rates rise and vice versa. In a low interest rate environment, risks associated with rising rates are heightened. Declines in dealer market-making capacity as a result of structural or regulatory changes could decrease liquidity and/or increase volatility in the fixed income markets. Markets for fixed income securities may decline significantly in response to adverse issuer, political, regulatory, market, economic or other developments that may cause broad changes in market value, public perceptions concerning these developments, and adverse investor sentiment or publicity. Similarly, environmental and public health risks, such as natural disasters, epidemics, pandemics or widespread fear that such events may occur, may impact markets adversely and cause market volatility in both the short- and long-term. In response to these events, the Fund’s value may fluctuate and/or the Fund may experience increased redemptions from shareholders, which may impact the Fund’s liquidity or force the Fund to sell securities into a declining or illiquid market.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Inflation Protected Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Inflation Protected Securities Risk — The value of inflation protected securities, including TIPS, generally will fluctuate in response to changes in “real” interest rates, generally decreasing when real interest rates rise and increasing when real interest rates fall. Real interest rates represent nominal (or stated) interest rates reduced by the expected impact of inflation. In addition, interest payments on inflation-indexed securities will generally vary up or down along with the rate of inflation.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Below Investment Grade Securities (Junk Bonds) Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Below Investment Grade Securities (Junk Bonds) Risk — Fixed income securities rated below investment grade (junk bonds) involve greater risks of default or downgrade and are generally more volatile than investment grade securities because the prospect for repayment of principal and interest of many of these securities is speculative. Because these securities typically offer a higher rate of return to compensate investors for these risks, they are sometimes referred to as “high yield bonds,” but there is no guarantee that an investment in these securities will result in a high rate of return.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Large Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Capitalization Risk — If valuations of large capitalization companies appear to be greatly out of proportion to the valuations of small or medium capitalization companies, investors may migrate to the stocks of small and medium sized companies. Additionally, larger, more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rates of successful smaller companies.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk — The risk that a change in interest rates will cause a fall in the value of fixed income securities, including U.S. Government securities, in which a Fund invests. Generally, the value of the Fund’s fixed income securities will vary inversely with the direction of prevailing interest rates. Changing interest rates may have unpredictable effects on the markets and may affect the value and liquidity of instruments held by the Fund. Although U.S. Government securities are considered to be among the safest investments, they are not guaranteed against price movements due to changing interest rates.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | U.S. Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

U.S. Government Securities Risk — Although U.S. Government securities are considered to be among the safest investments, they are still subject to the credit risk of the U.S. Government and are not guaranteed against price movements due to changing interest rates. Obligations issued by some U.S. Government agencies are backed by the U.S. Treasury, while others are backed solely by the ability of the agency to borrow from the U.S. Treasury or by the agency’s own resources. No assurance can be given that the U.S. Government will provide financial support to its agencies and instrumentalities if it is not obligated by law to do so.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Foreign Investment/Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Investment/Emerging Markets Risk — The risk that non-U.S. securities may be subject to additional risks due to, among other things, political, social and economic developments abroad, currency movements, and different legal, regulatory and tax, accounting and audit environments. These additional risks may be heightened with respect to emerging market countries because political turmoil and rapid changes in economic conditions are more likely to occur in these countries. Investments in emerging markets are subject to the added risk that information in emerging market investments may be unreliable or outdated due to differences in regulatory, accounting or auditing and financial record keeping standards, or because less information about emerging market investments is publicly available. In addition, the rights and remedies

associated with emerging market investments may be different than investments in developed markets. A lack of reliable information, rights and remedies increase the risks of investing in emerging markets in comparison to more developed markets. In addition, periodic U.S. Government restrictions on investments in issuers from certain foreign countries may require the Fund to sell such investments at inopportune times, which could result in losses to the Fund.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Foreign Sovereign Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Sovereign Debt Securities Risk — The risks that (i) the governmental entity that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or interest when it becomes due, because of factors such as debt service burden, political constraints, cash flow problems and other national economic factors; (ii) governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments; and (iii) there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Corporate Fixed Income Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Corporate Fixed Income Securities Risk — Corporate fixed income securities respond to economic developments, especially changes in interest rates, as well as perceptions of the creditworthiness and business prospects of individual issuers.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Commercial Paper Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commercial Paper Risk — Commercial paper is a short-term obligation with a maturity generally ranging from one to 270 days and is issued by U.S. or foreign companies or other entities in order to finance their current operations. Such investments are unsecured and usually discounted from their value at maturity. The value of commercial paper may be affected by changes in the credit rating or financial condition of the issuing entities and will tend to fall when interest rates rise and rise when interest rates fall. Asset-backed commercial paper may be issued by structured investment vehicles or other conduits that are organized to issue the commercial paper and to purchase trade receivables or other financial assets. The repayment of asset-backed commercial paper depends primarily on the cash collections received from such an issuer’s underlying asset portfolio and the issuer’s ability to issue new asset-backed commercial paper.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Investing in Limited Recourse Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investing in Limited Recourse Obligations Risk — Collateralized debt obligation (CDO) and collateralized loan obligation (CLO) securities are non-recourse obligations of their issuer payable solely from the related underlying collateral or its proceeds. Therefore, as a holder of CDOs and CLOs, the Fund must rely only on distributions on the underlying collateral or related proceeds for payment. If distributions on the underlying collateral are insufficient to make payments on the CDO or CLO securities, no other assets will be available for payment of the deficiency. As a result, the amount and timing of interest and principal payments in respect of CDO and CLO securities will depend on the performance and characteristics of the related underlying collateral.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Preferred Stock Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Stock Risk — Preferred stock represents an equity or ownership interest in an issuer that pays dividends at a specified rate and that has precedence over common stock in the payment of dividends. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of bonds take precedence over the claims of those who own preferred and common stock.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Depositary Receipts Risk — Depositary receipts, such as American Depositary Receipts, are certificates evidencing ownership of shares of a foreign issuer that are issued by depositary banks and generally trade on an established market. Depositary receipts are subject to many of the risks associated with investing directly in foreign securities, including, among other things, political, social and economic developments abroad, currency movements and different legal, regulatory, tax, accounting and audit environments.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Warrants Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Warrants Risk — Warrants are instruments that entitle the holder to buy an equity security at a specific price for a specific period of time. Warrants may be more speculative than other types of investments. The price of a warrant may be more volatile than the price of its underlying security, and a warrant may offer greater potential for capital appreciation as well as capital loss. A warrant ceases to have value if it is not exercised prior to its expiration date.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Tax Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Tax Risk — The Fund may gain most of its exposure to the commodities markets through its investment in the Subsidiary, which invests in commodity investments and derivative instruments. The Fund’s investment in the Subsidiary is expected to provide the Fund with exposure to the commodities markets within the limitations of the federal tax requirements of Subchapter M of the Code for qualification as a RIC. To the extent the Fund invests in such instruments directly, it will seek to restrict the resulting income from commodity-linked derivative instruments that do not generate qualifying income, such as commodity-linked swaps, to a

maximum of 10% of its gross income (when combined with its other investments that produce non-qualifying income) to comply with the qualifying income test necessary for the Fund to qualify as a RIC under Subchapter M of the Code. However, the Fund may generate more non-qualifying income than anticipated, may not be able to generate qualifying income in a particular taxable year at levels sufficient to meet the qualifying income requirement, or may not be able to accurately predict the non-qualifying income from these investments. Accordingly, the extent to which the Fund invests in commodities or commodity-linked derivative instruments directly may be limited by the requirements of Subchapter M of the Code, which the Fund must continue to satisfy to maintain its status as a RIC. Failure to comply with such requirements could have significant negative consequences to Fund shareholders. Under certain circumstances, the Fund may be able to cure a failure to meet the qualifying income requirement, but in order to do so the Fund may incur significant Fund-level taxes, which would effectively reduce (and could eliminate) the Fund’s returns. See the “Taxes” section of the SAI for additional information.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk — As a result of the Fund’s investments in securities or other investments denominated in, and/or receiving revenues in, foreign currencies and the Fund’s active management of its currency exposures, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected. Due to the Fund’s active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | REITs Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

REITs Risk — REITs are trusts that invest primarily in commercial real estate or real estate-related loans. The Fund’s investments in REITs will be subject to the risks associated with the direct ownership of real estate. Risks commonly associated with the direct ownership of real estate are described above. Some REITs may have limited diversification and may be subject to risks inherent in financing a limited number of properties.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Small and Medium Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Small and Medium Capitalization Risk — The small and medium capitalization companies in which the Fund may invest may be more vulnerable to adverse business or economic events than larger, more established companies. In particular, smaller companies may have limited product lines, markets and financial resources and may depend upon a relatively small management group. Therefore, small capitalization and medium capitalization stocks may be more volatile than those of larger companies. Small capitalization and medium

capitalization stocks may be traded over-the-counter (OTC). OTC stocks may trade less frequently and in smaller volume than exchange listed stocks and may have more price volatility than that of exchange-listed stocks.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Short Sales Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Short Sales Risk — A short sale involves the sale of a security that the Fund does not own in the expectation of purchasing the same security (or a security exchangeable therefore) at a later date at a lower price. Short sales expose the Fund to the risk that it will be required to buy the security sold short (also known as “covering” the short position) at a time when the security has appreciated in value, thus resulting in a loss to the Fund. Investment in short sales may also cause the Fund to incur expenses related to borrowing securities. Reinvesting proceeds received from short selling may create leverage, which can amplify the effects of market volatility on the Fund’s share price. In addition, shorting a future contract may require posting only a margin that may amount to less than the notional exposure of the contract. Such a practice may exacerbate the loss in a case of adverse price action.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Real Estate Industry Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Real Estate Industry Risk — Securities of companies principally engaged in the real estate industry may be subject to the risks associated with direct ownership of real estate, including fluctuations in the value of underlying properties and defaults by borrowers or tenants, changes in interest rates and risks related to general or local economic conditions.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk — The Fund’s use of futures, forwards, options and swaps is subject to market risk, leverage risk, correlation risk and liquidity risk. Leverage risk and liquidity risk are described below, and market risk is described above. Many OTC derivative instruments will not have liquidity beyond the counterparty to the instrument. Correlation risk is the risk that changes in the value of the derivative may not correlate perfectly with the underlying asset, rate or index. The Fund’s use of OTC forwards, options and swaps is also subject to credit risk and valuation risk. Credit risk is described below. Valuation risk is the risk that the derivative may be difficult to value and/or valued incorrectly. Each of these risks could cause the Fund to lose more than the principal amount invested in a derivative instrument. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment. The other parties to certain derivative contracts present the same types of credit risk as issuers of fixed income securities. The Fund’s use of derivatives may also increase the amount of taxes payable by shareholders. Both U.S. and non-U.S. regulators have adopted and implemented regulations governing derivatives markets, the ultimate impact of which remains unclear.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Commodity-Linked Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commodity-Linked Securities Risk — Investments in commodity-linked securities may be more volatile and less liquid than direct investments in the underlying commodities themselves. Commodity-related equity returns can also be affected by the issuer’s financial structure or the performance of unrelated businesses.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Investment Company Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company Risk — When the Fund invests in an investment company, it will bear a pro rata portion of the investment company’s expenses in addition to directly bearing the expenses associated with its own operations. Furthermore, while the risks of owning shares of an investment company generally reflect the risks of owning the underlying investments of the investment company, the Fund may be subject to additional or different risks than if the Fund had invested directly in the underlying investments. For example, the lack of liquidity in an ETF could result in its value being more volatile than that of the underlying portfolio securities.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Investment in the Subsidiary Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment in the Subsidiary Risk — The Subsidiary is not registered under the Investment Company Act of 1940, as amended (the 1940 Act), and, unless otherwise noted in this prospectus, is not subject to all of the investor protections of the 1940 Act. Thus, the Fund, as an investor in the Subsidiary, will not have all of the protections offered to investors in registered investment companies. In addition, changes in the laws of the United States and/or the Cayman Islands, under which the Fund and the Subsidiary, respectively, are organized, could result in the inability of the Fund and/or the Subsidiary to operate as intended and could negatively affect the Fund and its shareholders.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Commodity Investments and Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Commodity Investments and Derivatives Risk — Commodity investments and derivatives may be more volatile and less liquid than direct investments in the underlying commodities themselves. Commodity-related equity returns can also be affected by the issuer’s financial structure or the performance of unrelated businesses. The

value of a commodity investment or a derivative investment in commodities is typically based upon the price movements of a physical commodity, a commodity futures contract or commodity index or some other readily measurable economic variable that is dependent upon changes in the value of commodities or the commodities markets. The value of these securities will rise or fall in response to changes in the underlying commodity or related benchmark or investment, changes in interest rates or factors affecting a particular industry or commodity, such as natural disasters, weather and U.S. and international economic, political and regulatory developments.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Repurchase Agreements and Reverse Repurchase Agreements Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Repurchase Agreements and Reverse Repurchase Agreements Risk — In the event of the insolvency of the counterparty to a repurchase agreement or reverse repurchase agreement, recovery of the repurchase price owed to the Fund or, in the case of a reverse repurchase agreement, the securities sold by the Fund, may be delayed. Because reverse repurchase agreements may be considered to be the practical equivalent of borrowing funds, they constitute a form of leverage. If the Fund reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Fund’s yield.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Asset-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Asset-Backed Securities Risk — Payment of principal and interest on asset-backed securities is dependent largely on the cash flows generated by the assets backing the securities. Securitization trusts generally do not have any assets or sources of funds other than receivables and related property they own, and asset-backed securities are generally not insured or guaranteed by the related sponsor or any other entity. Asset-backed securities may be more illiquid than more conventional types of fixed income securities that the Fund may acquire.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Mortgage-Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Mortgage-Backed Securities Risk — Mortgage-backed securities are affected significantly by the rate of prepayments and modifications of the mortgage loans backing those securities, as well as by other factors such as borrower defaults, delinquencies, realized or liquidation losses and other shortfalls. Mortgage-backed securities are particularly sensitive to prepayment risk, which is described below, given that the term to maturity for mortgage loans is generally substantially longer than the expected lives of those securities;

however, the timing and amount of prepayments cannot be accurately predicted. The timing of changes in the rate of prepayments of the mortgage loans may significantly affect the Fund’s actual yield to maturity on any mortgage-backed securities, even if the average rate of principal payments is consistent with the Fund’s expectation. Along with prepayment risk, mortgage-backed securities are significantly affected by interest rate risk, which is described above. In a low interest rate environment, mortgage loan prepayments would generally be expected to increase due to factors such as refinancings and loan modifications at lower interest rates. In contrast, if prevailing interest rates rise, prepayments of mortgage loans would generally be expected to decline and therefore extend the weighted average lives of mortgage-backed securities held or acquired by the Fund.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk — The risk that certain securities may be difficult or impossible to sell at the time and the price that the Fund would like. The Fund may have to lower the price of the security, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Fund management or performance.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk — The Fund’s use of derivatives and repurchase agreements (which effectively constitute a form of borrowing) may result in the Fund’s total investment exposure substantially exceeding the value of its portfolio securities and the Fund’s investment returns depending substantially on the performance of securities that the Fund may not directly own. The use of leverage can amplify the effects of market volatility on the Fund’s share price and may also cause the Fund to liquidate portfolio positions when it would not be advantageous to do so in order to satisfy its obligations. The Fund’s use of leverage may result in a heightened risk of investment loss.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Opportunity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Opportunity Risk — The risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in other investments.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk — The risk that the issuer of a security or the counterparty to a contract will default or otherwise become unable to honor a financial obligation.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Duration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Duration Risk — The longer-term securities in which the Fund may invest are more volatile. A portfolio with a longer average portfolio duration is more sensitive to changes in interest rates than a portfolio with a shorter average portfolio duration.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Extension Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Extension Risk — The risk that rising interest rates may extend the duration of a fixed income security, typically reducing the security’s value.

MULTI-ASSET REAL RETURN FUND | SIIT Multi-Asset Real Return Fund | Prepayment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Prepayment Risk — The risk that, with declining interest rates, fixed income securities with stated interests may have the principal paid earlier than expected, requiring the Fund to invest the proceeds at generally lower interest rates.