v3.26.3
Label Element Value
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk/Return [Heading] oef_RiskReturnHeading The Core Fixed Income Portfolio
Objective [Heading] oef_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] oef_ObjectivePrimaryTextBlock

The investment objective of The Core Fixed Income Portfolio is to provide a high level of current income consistent with the preservation of capital.
Expense Heading [Optional Text] oef_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] oef_ExpenseNarrativeTextBlock

The fee and expense tables below describe the fees and expenses that you may pay if you buy and hold shares of the Portfolio.
Shareholder Fees Caption [Optional Text] oef_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Optional Text] oef_OperatingExpensesCaption Annual Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Expenses Restated to Reflect Current [Text] oef_ExpensesRestatedToReflectCurrent Total Annual Fund Operating Expenses have been restated to reflect current expenses as of June 30, 2026.
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 Portfolio with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes the reinvestment of all dividends and distributions in shares of the Portfolio and that your investment has a 5% return each year and that the Portfolio’s Total Annual Operating Expenses remain the same. Although your actual cost may be higher or lower, based on these assumptions, your cost would be:
Portfolio Turnover [Heading] oef_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] oef_PortfolioTurnoverTextBlock

The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” investments in its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These costs, which are not reflected in the Total Annual Operating Expenses or in the Example, affect the Portfolio’s performance. During the most recent fiscal year, the Portfolio’s turnover was 23% of the average value of its portfolio.
Portfolio Turnover, Rate oef_PortfolioTurnoverRate 23.00%
Strategy [Heading] oef_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] oef_StrategyNarrativeTextBlock

Under normal circumstances, the Portfolio invests primarily (i.e., at least 80% of its net assets) in fixed income securities. In the unlikely event that a change in this investment policy is adopted by the Board of Trustees, shareholders will receive at least 60 days prior written notice before such change is implemented. The Portfolio, under normal circumstances, invests predominantly in fixed income securities that, at the time of purchase, are rated in one of four highest rating categories assigned by one of the major independent rating agencies (“Baa” or higher by Moody’s Investors Service, “BBB” or higher by S&P Global Ratings) or are, in the view of the Specialist Manager, deemed to be of comparable quality. Securities in the fourth highest rating category may have speculative characteristics. From time to time, a substantial portion of the Portfolio, a diversified investment company, may be invested in any of the following: (1) investment grade mortgage-backed or asset-backed securities; (2) securities issued or fully guaranteed by the U.S. Government, Federal Agencies, or sponsored agencies; (3) investment grade fixed income securities issued by U.S. corporations; or (4) municipal bonds (i.e., debt securities issued by municipalities and related entities). Under normal conditions, the Portfolio may invest up to 20% of its assets in high yield securities (“junk bonds”) as well as cash or money market instruments in order to maintain liquidity, or in the event that the Specialist Manager determines that securities meeting the Portfolio’s investment objective and policies are not otherwise readily available for purchase. The Portfolio may invest in securities issued by other investment companies, including ETFs, that invest in fixed income securities. Consistent with its investment policies, the Portfolio may purchase and sell securities without regard to the effect on portfolio turnover. Securities purchased for the Portfolio will have varying maturities, but under normal circumstances the Portfolio will have an effective dollar weighted average portfolio maturity that is within the range of the average

portfolio maturity in the Bloomberg U.S. Aggregate Bond Index, which range, as of June 30, 2026, was between 0 and 96 years. The weighted average maturity of the Bloomberg U.S. Aggregate Bond Index as of June 30, 2026 was 8.33 years. The Portfolio may engage in transactions involving instruments such as option or futures contracts, in order to hedge against investment risks, seek to efficiently obtain or adjust exposure to certain securities or groups of securities, or otherwise to increase returns. The Portfolio may also write (sell) call options and put options, in order to receive premiums, on individual securities, market indexes, and/or on substitutes for such indexes, which may include futures contracts or ETFs. The Portfolio normally writes covered call and put options which have an initial maturity of up to nine months and that are “out of the money” at the time of initiation such that the call options sold generally will be above the current price level of the index when written and the exercise price of put options sold generally will be below the current price level of the index when written. In accordance with applicable interpretations of the SEC, certain derivative instruments may be counted as fixed income securities for purposes of the Portfolio’s policies regarding investments in fixed income securities, to the extent that such derivative instruments have economic characteristics similar to those of fixed income securities.

The Portfolio is authorized to operate on a multi-manager basis. This means that a single Portfolio may be managed by more than one Specialist Manager. The multi-manager structure is generally designed to provide investors access to broadly diversified investment styles. The Trust seeks to engage skilled Specialist Managers to provide a broad exposure to the relevant asset class and returns in excess of the Portfolio’s benchmark over time.
Summary of Definition of Rule 35d-1 Term in Fund Name [Text Block] fnd_NmRule35d1TermDfnSmryTextBlock The Portfolio, under normal circumstances, invests predominantly in fixed income securities that, at the time of purchase, are rated in one of four highest rating categories assigned by one of the major independent rating agencies (“Baa” or higher by Moody’s Investors Service, “BBB” or higher by S&P Global Ratings) or are, in the view of the Specialist Manager, deemed to be of comparable quality. Securities in the fourth highest rating category may have speculative characteristics. From time to time, a substantial portion of the Portfolio, a diversified investment company, may be invested in any of the following: (1) investment grade mortgage-backed or asset-backed securities; (2) securities issued or fully guaranteed by the U.S. Government, Federal Agencies, or sponsored agencies; (3) investment grade fixed income securities issued by U.S. corporations; or (4) municipal bonds (i.e., debt securities issued by municipalities and related entities). Under normal conditions, the Portfolio may invest up to 20% of its assets in high yield securities (“junk bonds”) as well as cash or money market instruments in order to maintain liquidity, or in the event that the Specialist Manager determines that securities meeting the Portfolio’s investment objective and policies are not otherwise readily available for purchase.
Summary of Selection Criteria for Rule 35d-1 Term in Fund Name [Text Block] fnd_NmRule35d1TermSlctnCritSmryTextBlock The Portfolio may invest in securities issued by other investment companies, including ETFs, that invest in fixed income securities. Consistent with its investment policies, the Portfolio may purchase and sell securities without regard to the effect on portfolio turnover.
Rule 35d-1 Eighty Percent Investment Policy [Text Block] fnd_NmRule35d1EightyPctInvstmntPlcyTextBlock Under normal circumstances, the Portfolio invests primarily (i.e., at least 80% of its net assets) in fixed income securities.
Bar Chart and Performance Table [Heading] oef_BarChartAndPerformanceTableHeading Performance Bar Chart and Table
Performance Narrative [Text Block] oef_PerformanceNarrativeTextBlock

Performance. The chart and table below show how The Core Fixed Income Portfolio has performed, and how its performance has varied, from year to year. The bar chart shows returns on a before-tax basis and gives some indication of risk by showing changes in the Portfolio’s yearly performance for each of the last ten full calendar years. The table accompanying the bar chart compares the Portfolio’s performance over time on a before and after-tax basis to that of a broad based market index. Of course, past performance, before and after taxes, does not indicate how the Portfolio will perform in the future.
Performance Information Illustrates Variability of Returns [Text] oef_PerformanceInformationIllustratesVariabilityOfReturns The chart and table below show how The Core Fixed Income Portfolio has performed, and how its performance has varied, from year to year. The bar chart shows returns on a before-tax basis and gives some indication of risk by showing changes in the Portfolio’s yearly performance for each of the last ten full calendar years.
Performance Past Does Not Indicate Future [Text] oef_PerformancePastDoesNotIndicateFuture Of course, past performance, before and after taxes, does not indicate how the Portfolio will perform in the future.
Bar Chart [Heading] oef_BarChartHeading Year-by-Year Total Returns as of 12/31*
Bar Chart Footnotes [Text Block] oef_BarChartFootnotesTextBlock

* Results shown on a calendar year basis; the Portfolio’s fiscal year, however, is June 30.
Bar Chart Closing [Text Block] oef_BarChartClosingTextBlock

The Portfolio’s before-tax return for the period from January 1, 2026 through September 30, 2026 (non-annualized) was ‑3.70%.

 

Best quarter:

 

4th Qtr. 2023

5.61%

 

 

Worst quarter:

 

1st Qtr. 2022

‑6.31%

 
Year to Date Return, Label [Optional Text] oef_YearToDateReturnLabel before-tax return
Bar Chart, Year to Date Return, Date oef_BarChartYearToDateReturnDate Sep. 30, 2026
Bar Chart, Year to Date Return oef_BarChartYearToDateReturn (3.70%)
Highest Quarterly Return, Label [Optional Text] oef_HighestQuarterlyReturnLabel Best quarter:
Highest Quarterly Return, Date oef_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return oef_BarChartHighestQuarterlyReturn 5.61%
Lowest Quarterly Return, Label [Optional Text] oef_LowestQuarterlyReturnLabel Worst quarter:
Lowest Quarterly Return, Date oef_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return oef_BarChartLowestQuarterlyReturn (6.31%)
Performance Table Heading oef_PerformanceTableHeading Average Annual Total Returns (for the periods ended 12/31/25)
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 Actual after-tax returns depend on an investor’s tax situation and may differ from those shown, and after-tax returns shown are not relevant to investors who hold Portfolio shares through tax-advantaged arrangements, such as qualified retirement plans.
Performance Table Closing [Text Block] oef_PerformanceTableClosingTextBlock

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. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown, and after-tax returns shown are not relevant to investors who hold Portfolio shares through tax-advantaged arrangements, such as qualified retirement plans.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Risk Lose Money [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock There is no guarantee that the Portfolio will achieve its investment objective and, as is the case with any investment, you may lose money on your investment in the Portfolio.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Multi-Manager Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Multi-Manager Risk – the Portfolio’s multi-manager structure involves the risk that the Specialist Managers serving the Portfolio do not achieve favorable investment results relative to other investments or that the Portfolio’s assets are not effectively allocated among Specialist Managers in a manner that enhances the Portfolio’s total return or reduces the volatility that might be expected of any one management style. Additionally, the multi-manager structure may, under certain circumstances, cause the Portfolio to incur higher trading costs than might occur in a fund served by a single investment adviser.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Passive Investing Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Passive Investing Risk – the Portfolio may employ a passive investment approach, which attempts to approximate as closely as practicable, before expenses, the performance of either the Portfolio’s benchmark index, or one or more identifiable subsets or other portions of that index as deemed appropriate by the Adviser, regardless of the current or projected performance of a specific security or a particular industry or market sector. Maintaining investments in securities regardless of market conditions or the performance of individual securities could cause the Portfolio’s return to be lower than if the Portfolio employed an active strategy. In addition, the Portfolio’s return may not match or achieve a high degree of correlation with the return of the target investment pool due to operating expenses, transaction costs, and cash flows.

Additionally, the range of securities in which the Portfolio may invest, and the several investment strategies that may be used in seeking to achieve the Portfolio’s objective, involve additional risks. These are summarized below.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Fixed Income Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Fixed Income Risk.  Investments in fixed income securities may involve the following risks, depending on the instrument involved:
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Credit Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Credit Risk – An investment in the Portfolio also involves the risk that the issuer of a fixed income

security that the Portfolio holds will fail to make timely payments of interest or principal, or go bankrupt, or that the value of the securities will decline because of a market perception that the issuer may not make payments on time, thus potentially reducing the Portfolio’s return. Changes in economic conditions are likely to cause issuers of these fixed income securities to be unable to meet their obligations. The lower the rating of a debt security, the higher its credit risk. In addition, the securities of many U.S. Government agencies, authorities or instrumentalities in which the Portfolio may invest are neither issued nor guaranteed by the U.S. Government, and may be supported only by the ability of the issuer to borrow from the U.S. Treasury or by the credit of the issuer.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Interest Rate Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Interest Rate Risk – The value of fixed income securities held in the Portfolio, including U.S. Government securities, may decline with changes in interest rates. Prices of fixed income securities with longer effective maturities are more sensitive to interest rate changes than those with shorter effective maturities. U.S. Government securities can exhibit price movements resulting from changes in interest rates. During low interest rate environments, the risk that interest rates will rise is increased. Such increases may expose fixed income markets to heightened volatility and reduced liquidity for certain fixed income investments, particularly those with longer maturities. These risks are greater when a low interest rate environment has existed for an extended period of time.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Asset-Backed/Mortgage-Backed Security Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Asset-Backed/Mortgage-Backed Security Risk – The market value and yield of asset-backed and mortgage-backed securities can vary due to market interest rate fluctuations and early prepayments of underlying instruments. Although these securities may offer yields higher than those available from other types of securities, these securities may be less effective than other types of securities as a means of “locking in” attractive long-term rates because of the prepayment feature. During periods of difficult

or frozen credit markets, significant changes in interest rates, or deteriorating economic conditions, such securities may decline in value, face valuation difficulties, become more volatile and/or become illiquid. Mortgage-backed securities may be particularly susceptible to Prepayment Risk.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Call/Prepayment Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Call/Prepayment Risk – When interest rates are declining, issuers of securities held by the Portfolio may prepay principal earlier than scheduled. As a result of this risk, the Portfolio may have to reinvest these prepayments at those lower rates, thus reducing its income. Mortgage-backed and asset-backed securities are especially sensitive to prepayment.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Extension Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Extension Risk – These securities are also subject to the risk that payment on the loans underlying the securities held by the Portfolio will be made more slowly when interest rates are rising. This could cause the market value of the securities to decline.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Liquidity Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Liquidity Risk – At times, certain securities may be difficult or impossible to sell at the price that would normally prevail in the market. The seller may have to lower the price, sell other securities instead or forego an investment opportunity, any of which could have a negative effect on Portfolio management or performance. This includes the risk of missing out on an investment opportunity because the assets necessary to take advantage of it are tied up in less advantageous investments.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Municipal Bond Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Municipal Bond Risk – The risk of a municipal obligation generally depends on the financial and credit status of the issuer. Constitutional amendments, legislative enactments, executive orders, administrative regulations, voter initiatives, and the issuer’s regional economic conditions may affect the municipal security’s value, interest payments, repayment of principal and the Portfolio’s ability to sell the security. Failure of a municipal security issuer to comply with applicable tax requirements may make income paid thereon taxable, resulting in a decline in the security’s value. In addition, there could be changes in applicable tax laws or tax treatments that reduce or eliminate the current federal income tax exemption on municipal securities or otherwise adversely affect the current federal or state tax status of municipal securities. Portfolio dividends derived from certain “private activity” municipal securities generally will constitute an item of tax preference includable in alternative minimum taxable income for both corporate and non-corporate taxpayers.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | High Yield Bond Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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High Yield Bond Risk – High yield bonds, commonly referred to as “junk bonds,” are considered speculative under traditional investment standards. Prices of these securities will rise and fall primarily in response to changes in the issuer’s financial health, although changes in market interest rates also will affect prices. High yield bonds may also experience reduced liquidity, and sudden and substantial decreases in price, during certain market conditions.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Investment in Other Investment Companies Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Investment in Other Investment Companies Risk – As with other investments, investments in other investment companies are subject to market and selection risk. To the extent that the Portfolio acquires shares of investment companies, shareholders bear both their proportionate share of expenses in the Portfolio (including management and advisory fees) and, indirectly, the expenses of the acquired investment companies.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Exchange-Traded Funds Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Exchange-Traded Funds Risk – In addition to the risks of investing in other investment companies generally, an investment in securities issued by an ETF may be subject to the following risks: (1) shares of the ETF may trade at a discount to its net asset value; (2) an active trading market for the ETF’s shares may not develop; (3) the exchange on which the ETF is listed may, under certain circumstances, suspend trading of the ETF’s shares; and (4) to the extent that an ETF is acquired in order to track a specific asset or index, the ETF may fail to effectively accomplish that goal.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Risks Associated with Investments in Derivatives [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Risks Associated with Investments in Derivatives.  The Portfolio is permitted to invest in derivative instruments, including options, futures and options on futures, swaps, structured notes and currency forwards. Investment in derivatives depends largely on the performance of an underlying reference instrument or rate and the Specialist Manager’s ability to predict correctly the direction of securities prices, interest rates, currency exchange rates and/or other economic factors. Derivatives involve additional costs and often have risks similar to an investment in the reference instrument in addition to other risks, such as:
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | General Derivative Risks [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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General Derivative Risks – Derivatives may be volatile and may involve significant risks. The Portfolio’s exposure to derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other investments. The underlying security, measure or other instrument on which a derivative is based, or the derivative itself, may not perform as expected, and hedging positions may not correlate closely with the

instruments or exposures being hedged. Normally derivatives involve leverage, which means that their use can significantly magnify the effect of price movements of the underlying securities or reference measures, disproportionately increasing the Portfolio’s losses and reducing the Portfolio’s opportunities for gains. Some derivatives have the potential for unlimited loss, including a loss that may be greater than the amount invested. Derivatives also present default risks if the counterparty to a derivatives contract fails to fulfill its obligations to the Portfolio. Certain derivatives held by the Portfolio may be illiquid, including non-exchange-traded or over-the-counter derivatives that are linked to illiquid instruments or illiquid markets, making it difficult to close out an unfavorable position. Derivatives also may be more difficult to purchase, sell or value than other instruments. Derivatives risk may be more significant when derivatives are used to enhance return or as a substitute for a cash investment position, rather than solely to hedge the risk of a position held by the Portfolio.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Counterparty Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Counterparty Risk – The Portfolio will be subject to counterparty credit risk with respect to derivative contracts entered into by the Portfolio or held by special purpose or structured vehicles in which the Portfolio invests, including other investment companies. If a counterparty becomes bankrupt or otherwise fails to perform its obligations due to financial difficulties, the Portfolio may experience significant delays in obtaining any recovery in a bankruptcy or other reorganization proceeding. The Portfolio may obtain only a limited recovery or may obtain no recovery in such circumstances.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Derivatives Tax Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Derivatives Tax Risk – Compared to other types of investments, derivatives may be less tax efficient. In addition, changes in government regulation of derivative instruments could affect the character, timing and amount of the Portfolio’s taxable income or gains, and may limit or prevent the Portfolio’s use of certain derivative instruments, which could make the investment strategy more costly to implement or require the Portfolio to change its investment strategy. These rules may: (i) affect whether gains and losses recognized by the Portfolio are treated as ordinary or capital or as short-term or long-term, (ii) accelerate the recognition of income or gains to the Portfolio, (iii) defer losses to the Portfolio, and (iv) cause adjustments in the holding periods of the Portfolio’s securities. The Portfolio’s use of derivatives may be limited by the requirements for taxation of the Portfolio as a regulated investment company.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Options Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Options Risk – Purchasing and writing put and call options are specialized activities that may entail greater-than-ordinary investment risks and are considered speculative. An option gives the purchaser, in exchange for a premium, the right, but not the obligation, to buy (a “call option”) or sell (a “put option”) an underlying security or futures contract – or receive a cash settlement based on an underlying asset, rate or index – at a specified price during a specified period or on a specified date. When the Portfolio writes an option, it retains the premium if the option expires unexercised but may incur a net loss if the cost of satisfying its obligations exceeds the premium received. A written call option exposes the Portfolio to the risk that it will be required to sell the underlying instrument below its market value, while a written put option exposes the Portfolio to the risk that it will be required to purchase the underlying instrument above its market value. When the Portfolio purchases an option, it may lose some or all of the premium if the underlying instrument does not move sufficiently in the anticipated direction, including the entire premium if the option expires without being sold or exercised. Options written on instruments intended to replicate an index present the same risks, and those instruments may not closely track the index.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Options Writing Strategy Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Options Writing Strategy Risk – if the underlying index appreciates or depreciates sufficiently over the period to offset the new premium received from the written option on that index, a net loss will result. In addition, the Portfolio may write options on index substitutes, which are subject to the same risks as index options. I The value of the index substitute is subject to change as the values of the component securities fluctuate and the performance of the index substitute may not exactly match the performance of the index.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | Futures Risk [Member]  
Prospectus [Line Items] oef_ProspectusLineItems  
Risk [Text Block] oef_RiskTextBlock

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Futures Risk – there can be no assurance that price movements in the futures markets will correlate with the prices of the underlying securities positions. Additionally, price distortions could result if investors in the futures markets opt to make or take delivery of the underlying securities rather than engage in closing transactions because such trend might result in a reduction in the liquidity of the futures market. Further, an increase in the participation of speculators in the futures market could cause temporary price distortions.
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | The Core Fixed Income Portfolio  
Prospectus [Line Items] oef_ProspectusLineItems  
Maximum Deferred Sales Charge (as a percentage of Offering Price) oef_MaximumDeferredSalesChargeOverOfferingPrice 0.00%
Redemption Fee (as a percentage of Amount Redeemed) oef_RedemptionFeeOverRedemption 0.00%
Management Fees (as a percentage of Assets) oef_ManagementFeesOverAssets 0.06%
Other Expenses (as a percentage of Assets): oef_OtherExpensesOverAssets 0.09%
Acquired Fund Fees and Expenses oef_AcquiredFundFeesAndExpensesOverAssets 0.03%
Expenses (as a percentage of Assets) oef_ExpensesOverAssets 0.18% [1]
Expense Example, with Redemption, 1 Year oef_ExpenseExampleYear01 $ 18
Expense Example, with Redemption, 3 Years oef_ExpenseExampleYear03 58
Expense Example, with Redemption, 5 Years oef_ExpenseExampleYear05 101
Expense Example, with Redemption, 10 Years oef_ExpenseExampleYear10 $ 230
The Core Fixed Income Portfolio | Bloomberg U.S. Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.30%
Average Annual Return, Percent oef_AvgAnnlRtrPct (0.36%)
Average Annual Return, Percent oef_AvgAnnlRtrPct 2.01%
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio  
Prospectus [Line Items] oef_ProspectusLineItems  
Annual Return [Percent] oef_AnnlRtrPct 3.24%
Annual Return [Percent] oef_AnnlRtrPct 3.61%
Annual Return [Percent] oef_AnnlRtrPct (0.61%)
Annual Return [Percent] oef_AnnlRtrPct 9.20%
Annual Return [Percent] oef_AnnlRtrPct 7.88%
Annual Return [Percent] oef_AnnlRtrPct (1.76%)
Annual Return [Percent] oef_AnnlRtrPct (13.43%)
Annual Return [Percent] oef_AnnlRtrPct 5.23%
Annual Return [Percent] oef_AnnlRtrPct 1.21%
Annual Return [Percent] oef_AnnlRtrPct 7.03%
Average Annual Return, Percent oef_AvgAnnlRtrPct 7.03%
Average Annual Return, Percent oef_AvgAnnlRtrPct (0.62%)
Average Annual Return, Percent oef_AvgAnnlRtrPct 1.96%
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | After Taxes on Distributions  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Percent oef_AvgAnnlRtrPct 5.49%
Average Annual Return, Percent oef_AvgAnnlRtrPct (1.88%)
Average Annual Return, Percent oef_AvgAnnlRtrPct 0.77%
The Core Fixed Income Portfolio | The Core Fixed Income Portfolio | After Taxes on Distributions and Sales  
Prospectus [Line Items] oef_ProspectusLineItems  
Average Annual Return, Percent oef_AvgAnnlRtrPct 4.14%
Average Annual Return, Percent oef_AvgAnnlRtrPct (0.99%)
Average Annual Return, Percent oef_AvgAnnlRtrPct 1.01%
[1] Total Annual Fund Operating Expenses have been restated to reflect current expenses as of June 30, 2026.