Shares [Member] Investment Risks - Shares [Member] - Treasury Instruments Portfolio |
Nov. 30, 2025 |
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| Interest Rate Risk [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | INTEREST RATE RISK is the risk that during periods of rising interest rates, the market value of the Portfolio’s securities will tend to be lower than prevailing market rates and in periods of falling interest rates, the market value of the Portfolio’s securities will tend to be higher. The Portfolio’s yield will vary as short-term securities in its portfolio mature and the proceeds are reinvested in securities with different interest rates. In general, securities with longer maturities or durations are more sensitive to interest rate changes. A general rise in interest rates may cause investors to move out of fixed income securities on a large scale, which could adversely affect the price and liquidity of fixed income securities and could also result in increased redemptions for the Portfolio. During periods when inflation rates are high or rising, or during periods of low interest rates, the Portfolio may be subject to a greater risk of rising interest rates. Interest rate changes can be sudden and unpredictable and may have unpredictable effects on the markets and the Portfolio’s investment, may result in heightened market volatility, may impact the liquidity of fixed-income securities and of the Portfolio, and may detract from Portfolio performance.
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| CREDIT OR DEFAULT RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | CREDIT (OR DEFAULT) RISK is the risk that the inability or unwillingness of an issuer or guarantor of a fixed-income security, or a counterparty to a repurchase or other transaction, to meet its principal or interest payments or other financial obligations in a timely manner will adversely affect the value of the Portfolio’s investments and its returns. Changes in an issuer’s financial strength, the market’s perception of an issuer’s creditworthiness, or in the credit rating of the issuer or the security may also affect the value of the Portfolio’s investment in that issuer.
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| DEBT EXTENSION RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | DEBT EXTENSION RISK is the risk that when interest rates rise an issuer will exercise its right to pay principal on certain debt securities held by the Portfolio later than expected. This will cause the value of the security to decrease and the Portfolio may lose opportunities to invest in higher yielding securities.
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| VARIABLE OR FLOATING RATE INSTRUMENTS RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | VARIABLE OR FLOATING RATE INSTRUMENTS RISK is the risk that securities with variable or floating rates can be less sensitive to interest rate changes than securities with fixed interest rates, but may decline in value and negatively impact the Portfolio, particularly if changes in prevailing interest rates are more frequent or sudden than the rate changes for the variable or floating rate securities, which only occur periodically. Although variable and floating rate securities are less sensitive to interest rate risk than fixed-rate securities, they are subject to greater liquidity risk, which could impede their value.
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| INCOME RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | INCOME RISK is the risk that the Portfolio’s ability to distribute income to shareholders depends on the yield available from the Portfolio’s investments. Falling interest rates will cause the Portfolio’s income to decline. Income risk is generally higher for short-term debt securities.
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| LARGE SHAREHOLDER RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | LARGE SHAREHOLDER RISK is the risk that a large proportion of the interests of the Portfolio may be held by a small number of investors (or a single investor) and the Portfolio may experience adverse effects when certain large shareholders, including funds or accounts over which the Portfolio’s investment adviser or an affiliate of the investment adviser has investment discretion, purchase or redeem large amounts of shares of the Portfolio. Such large shareholder redemptions, which may occur rapidly and unexpectedly, may cause the Portfolio to sell its securities at times it would not otherwise do so, which may negatively impact its liquidity and/or NAV. Such sales may also accelerate the realization of taxable income to shareholders if these sales result in gains, and may also increase transaction costs. In addition, large redemptions could lead to an increase in the Portfolio’s expense ratio due to expenses being allocated over a smaller asset base. Large purchases of the Portfolio’s shares or having a more concentrated shareholder base may also adversely affect the Portfolio’s performance to the extent that the Portfolio is delayed in investing new cash or otherwise maintains a larger cash position than it ordinarily would.
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| INVESTMENT COMPANY RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | INVESTMENT COMPANY RISK is the risk that the Portfolio will be subject to the risks associated with investments in registered investment companies (“Underlying Funds”), such as the possibility that the value of the securities or instruments held by the Underlying Funds could decrease. Investments in Underlying Funds may involve duplication of management fees and certain other expenses, as the Portfolio indirectly bears its proportionate share of any expenses paid by the Underlying Funds in which it invests. NTI may be subject to potential conflicts of interest with respect to investments in affiliated Underlying Funds, which are Underlying Funds managed by NTI or its affiliates, because the fees paid to NTI by some affiliated Underlying Funds may be higher than the fees paid by other Underlying Funds.
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| MARKET RISKS [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | MARKET RISK is the risk that the value of the Portfolio’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Portfolio may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, elevated levels of government debt, changes in interest rates, lack of liquidity in the bond or equity markets or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, changes in trade regulation or economic sanctions, internal unrest and discord, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions, the threat or occurrence of a government shutdown, or other events or adverse investor sentiment could have a significant impact on the Portfolio and its investments. During periods of market disruption or other abnormal market conditions, the Portfolio’s exposure to risks described elsewhere in this summary will likely increase.
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| CASH POSITIONS RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | CASH POSITIONS RISK is the risk that maintaining cash positions may negatively affect the Portfolio’s performance and potentially limit investment opportunities as a result of the Portfolio’s uninvested assets. Maintaining cash positions may also subject the Portfolio to increased credit risk exposure to the custodian bank.
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| MANAGEMENT RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | MANAGEMENT RISK is the risk that a strategy used by the Portfolio’s investment adviser may fail to produce the intended results or that imperfections, errors or limitations in the tools and data used by the investment adviser may cause unintended results.
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| STABLE NAV RISK [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | STABLE NAV RISK is the risk that the Portfolio will not be able to maintain a NAV per share of $1.00 at all times. A significant enough market disruption or drop in market prices of securities held by the Portfolio, especially at a time when the Portfolio needs to sell securities to meet shareholder redemption requests, could cause the value of the Portfolio’s shares to decrease to a price less than $1.00 per share. If the Portfolio fails to maintain a stable NAV (or if there is a perceived threat of such a failure) the Portfolio could be subject to increased redemption activity, which could adversely affect its NAV.
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| Risk Lose Money [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | You could lose money by investing in the Portfolio. |
| Risk Not Insured Depository Institution [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | An investment in the Portfolio is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank.
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| Risk Money Market Fund May Not Preserve Dollar [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | Although the Portfolio seeks to preserve the value of your investment at $1.00 per share, the Portfolio cannot guarantee it will do so. |
| Risk Money Market Fund Sponsor May Not Provide Support [Member] | |
| Prospectus [Line Items] | |
| Risk [Text Block] | The Portfolio’s sponsor is not required to reimburse the Portfolio for losses, and you should not expect that the sponsor will provide financial support to the Portfolio at any time, including during periods of market stress.
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