| Label | Element | Value |
|---|---|---|
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk/Return [Heading] | oef_RiskReturnHeading | U.S. EQUITY FACTOR ALLOCATION FUND |
| Objective [Heading] | oef_ObjectiveHeading | Investment Goal |
| Objective, Primary [Text Block] | oef_ObjectivePrimaryTextBlock | Long-term growth of capital and income. |
| Expense Heading [Optional Text] | oef_ExpenseHeading | Fees and Expenses |
| Expense Narrative [Text Block] | oef_ExpenseNarrativeTextBlock | This table describes the fees and expenses that you may pay if you buy, hold, and sell Fund shares. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in this table and examples below. |
| Operating Expenses Caption [Optional Text] | oef_OperatingExpensesCaption | ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment) |
| Expense Example [Heading] | oef_ExpenseExampleHeading | EXAMPLE |
| Expense Example Narrative [Text Block] | oef_ExpenseExampleNarrativeTextBlock | This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem or hold all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. |
| Expense Example by, Year, Caption [Text] | oef_ExpenseExampleByYearCaption | Although your actual costs may be higher or lower, based on these assumptions your costs would be: |
| Portfolio Turnover [Heading] | oef_PortfolioTurnoverHeading | PORTFOLIO TURNOVER |
| Portfolio Turnover [Text Block] | oef_PortfolioTurnoverTextBlock | The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual Fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 45% of the average value of its portfolio. |
| Portfolio Turnover, Rate | oef_PortfolioTurnoverRate | 45.00% |
| Strategy [Heading] | oef_StrategyHeading | Principal Investment Strategies |
| Strategy Narrative [Text Block] | oef_StrategyNarrativeTextBlock | Under normal market conditions, the Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity and equity-related securities, such as structured notes and convertible bonds, of U.S. companies of all capitalization ranges. The Fund may also, to a lesser extent, invest in American Depositary Receipts (ADRs) and interests in real estate investments trusts (REITs). The Fund’s investment portfolio will be diversified and will not be concentrated in any particular industry or sector. The Fund uses a quantitative-based, active stock selection investment strategy, which typically relies on a model-based approach to make investment decisions. The Fund quantitatively categorizes and selects securities based on certain characteristics (Factors) that are determined by SEI Investments Management Corporation (SIMC or the Adviser), such as volatility, share price performance, earnings, book value, revenues, cash flow or stock price. The Adviser uses its own judgment and model-based systems to assess which Factors to use and to determine what portion of the Fund’s assets should be invested in each security identified. However, based on perceived market opportunities, the Adviser may reallocate the Fund’s assets to tilt in favor of one or more Factors. The Adviser may add, remove or modify certain Factors in its model based on investment research or in response to changes in market conditions. |
| Summary of Definition of Rule 35d-1 Term in Fund Name [Text Block] | fnd_NmRule35d1TermDfnSmryTextBlock | The Fund may also, to a lesser extent, invest in American Depositary Receipts (ADRs) and interests in real estate investments trusts (REITs). The Fund’s investment portfolio will be diversified and will not be concentrated in any particular industry or sector. |
| Summary of Selection Criteria for Rule 35d-1 Term in Fund Name [Text Block] | fnd_NmRule35d1TermSlctnCritSmryTextBlock | The Fund uses a quantitative-based, active stock selection investment strategy, which typically relies on a model-based approach to make investment decisions. The Fund quantitatively categorizes and selects securities based on certain characteristics (Factors) that are determined by SEI Investments Management Corporation (SIMC or the Adviser), such as volatility, share price performance, earnings, book value, revenues, cash flow or stock price. |
| Rule 35d-1 Eighty Percent Investment Policy [Text Block] | fnd_NmRule35d1EightyPctInvstmntPlcyTextBlock | Under normal market conditions, the Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in equity and equity-related securities, such as structured notes and convertible bonds, of U.S. companies of all capitalization ranges. |
| Bar Chart and Performance Table [Heading] | oef_BarChartAndPerformanceTableHeading | Performance Information |
| Performance Narrative [Text Block] | oef_PerformanceNarrativeTextBlock | The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing the Fund’s performance for the past seven calendar years and by showing how the Fund’s average annual returns for 1 year and 5 years, and since the Fund’s inception, compare with those of a broad measure of market performance. The Fund’s past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. For current performance information, please call 1‑800-DIAL-SEI. |
| Performance Information Illustrates Variability of Returns [Text] | oef_PerformanceInformationIllustratesVariabilityOfReturns | The bar chart and the performance table below provide some indication of the risks of investing in the Fund by showing the Fund’s performance for the past seven calendar years and by showing how the Fund’s average annual returns for 1 year and 5 years, and since the Fund’s inception, compare with those of a broad measure of market performance. |
| Performance Additional Market Index [Text] | oef_PerformanceAdditionalMarketIndex | This table compares the Fund’s average annual total returns to those of a broad-based securities market index and an additional index with characteristics relevant to the Fund’s investment strategy. |
| Performance Availability Phone [Text] | oef_PerformanceAvailabilityPhone | 1‑800-DIAL-SEI |
| Performance Past Does Not Indicate Future [Text] | oef_PerformancePastDoesNotIndicateFuture | The Fund’s past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. |
| Bar Chart Closing [Text Block] | oef_BarChartClosingTextBlock | Best Quarter: 20.01% (6/30/20) |
| Year to Date Return, Label [Optional Text] | oef_YearToDateReturnLabel | total return |
| Bar Chart, Year to Date Return, Date | oef_BarChartYearToDateReturnDate | Jun. 30, 2026 |
| Bar Chart, Year to Date Return | oef_BarChartYearToDateReturn | 11.18% |
| Highest Quarterly Return, Label [Optional Text] | oef_HighestQuarterlyReturnLabel | Best Quarter: |
| Highest Quarterly Return, Date | oef_BarChartHighestQuarterlyReturnDate | Jun. 30, 2020 |
| Highest Quarterly Return | oef_BarChartHighestQuarterlyReturn | 20.01% |
| Lowest Quarterly Return, Label [Optional Text] | oef_LowestQuarterlyReturnLabel | Worst Quarter: |
| Lowest Quarterly Return, Date | oef_BarChartLowestQuarterlyReturnDate | Mar. 31, 2020 |
| Lowest Quarterly Return | oef_BarChartLowestQuarterlyReturn | (21.75%) |
| Performance Table Heading | oef_PerformanceTableHeading | Average Annual Total Returns (for the periods ended December 31, 2025) |
| Index No Deduction for Fees, Expenses, or Taxes [Text] | oef_IndexNoDeductionForFeesExpensesTaxes | (reflects no deduction for fees, expenses or taxes) |
| Performance Table Uses Highest Federal Rate | oef_PerformanceTableUsesHighestFederalRate | After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. |
| Performance Table Not Relevant to Tax Deferred | oef_PerformanceTableNotRelevantToTaxDeferred | Your actual after-tax returns will depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. |
| Performance Table Narrative | oef_PerformanceTableNarrativeTextBlock | This table compares the Fund’s average annual total returns to those of a broad-based securities market index and an additional index with characteristics relevant to the Fund’s investment strategy. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Risk Lose Money [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | You could lose money on your investment in the Fund, just as you could with other investments. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Risk Not Insured [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Market Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Large Capitalization Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Small and Medium Capitalization Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Investment Style Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Quantitative Investing Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Depositary Receipts Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Convertible and Preferred Securities Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | REITs Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Structured Securities Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | Liquidity Risk [Member] | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Risk [Text Block] | oef_RiskTextBlock | 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. |
| SIIT U.S. Equity Factor Allocation Fund | U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund - Class A | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Management Fees (as a percentage of Assets) | oef_ManagementFeesOverAssets | 0.25% |
| Distribution and Service (12b-1) Fees | oef_DistributionAndService12b1FeesOverAssets | 0.00% |
| Other Expenses (as a percentage of Assets): | oef_OtherExpensesOverAssets | 0.06% |
| Expenses (as a percentage of Assets) | oef_ExpensesOverAssets | 0.31% |
| Expense Example, with Redemption, 1 Year | oef_ExpenseExampleYear01 | $ 32 |
| Expense Example, with Redemption, 3 Years | oef_ExpenseExampleYear03 | 100 |
| Expense Example, with Redemption, 5 Years | oef_ExpenseExampleYear05 | 174 |
| Expense Example, with Redemption, 10 Years | oef_ExpenseExampleYear10 | $ 393 |
| U.S. EQUITY FACTOR ALLOCATION FUND | S&P 500 Index Return (reflects no deduction for fees, expenses or taxes) | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Average Annual Return, Label [Optional Text] | oef_AverageAnnualReturnLabel | S&P 500 Index Return (reflects no deduction for fees, expenses or taxes) |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 17.88% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 14.42% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 14.91% |
| U.S. EQUITY FACTOR ALLOCATION FUND | Russell 3000 Return (reflects no deduction for fees, expenses or taxes) | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Average Annual Return, Label [Optional Text] | oef_AverageAnnualReturnLabel | Russell 3000 Return (reflects no deduction for fees, expenses or taxes) |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 17.15% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 13.15% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 14.18% |
| U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund - Class A | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Annual Return [Percent] | oef_AnnlRtrPct | 28.11% |
| Annual Return [Percent] | oef_AnnlRtrPct | 13.17% |
| Annual Return [Percent] | oef_AnnlRtrPct | 32.97% |
| Annual Return [Percent] | oef_AnnlRtrPct | (15.77%) |
| Annual Return [Percent] | oef_AnnlRtrPct | 22.53% |
| Annual Return [Percent] | oef_AnnlRtrPct | 25.20% |
| Annual Return [Percent] | oef_AnnlRtrPct | 17.99% |
| Average Annual Return, Label [Optional Text] | oef_AverageAnnualReturnLabel | Return Before Taxes |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 17.99% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 15.18% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 14.16% |
| Performance Inception Date | oef_PerfInceptionDate | Apr. 26, 2018 |
| U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund - Class A | After Taxes on Distributions | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Average Annual Return, Label [Optional Text] | oef_AverageAnnualReturnLabel | Return After Taxes on Distributions |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 16.26% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 12.23% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 12.06% |
| U.S. EQUITY FACTOR ALLOCATION FUND | SIIT U.S. Equity Factor Allocation Fund - Class A | After Taxes on Distributions and Sales | ||
| Prospectus [Line Items] | oef_ProspectusLineItems | |
| Average Annual Return, Label [Optional Text] | oef_AverageAnnualReturnLabel | Return After Taxes on Distributions and Sale of Fund Shares |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 11.48% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 11.18% |
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 10.91% |