Label	Element	Value
Risk Return Abstract	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	NORTHWESTERN MUTUAL SERIES FUND INC
Prospectus Date	rr_ProspectusDate	May 01, 2024
Asset Allocation Portfolio
Risk Return Abstract	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Asset Allocation Portfolio – Summary
Objective [Heading]	rr_ObjectiveHeading	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">INVESTMENT OBJECTIVE</span>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to realize as high a level of total return as is consistent with reasonable investment risk.
Expense [Heading]	rr_ExpenseHeading	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">FEES AND EXPENSES OF THE PORTFOLIO</span>
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The table below describes the fees and expenses that you may pay when you buy and hold interests in a separate account that invests in shares of the Portfolio as a result of your purchase of a variable annuity contract or variable life insurance policy. The fees and expenses shown in the table and Example do not reflect fees and expenses separately charged by variable annuity contracts or variable life insurance policies. If the fees and expenses separately charged by variable annuity contracts and variable life insurance policies were included, the fees and expenses shown in the table and the Example would be higher.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;font-style:italic;font-weight:bold;margin-left:0.0pt;">Shareholder Fees</span><span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;margin-left:0.0pt;">(fees paid directly from your investment)</span>
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;font-style:italic;font-weight:bold;margin-left:0.0pt;">Annual Portfolio Operating Expenses</span><span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;margin-left:0.0pt;">(expenses that you pay each year as a percentage </span><span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;margin-left:0.0pt;">of the value of your investment)</span>
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;">April 30, 2025</span>
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	<span style="color:#000000;font-family:Times New Roman;font-size:10pt;font-style:italic;font-weight:bold;">Portfolio Turnover</span>
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in Annual Portfolio Operating Expenses or in the Example, affect the Portfolio’s performance. During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 10.57% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	10.57%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;">Includes fees and expenses incurred indirectly by the Portfolio as a result of investments in other investment companies (Acquired Fund Fees and Expenses). The operating expenses of the Portfolio reflected in the Portfolio's most recent annual report and Financial Highlights do not include the Acquired Fund Fees and Expenses.</span>
Expense Example [Heading]	rr_ExpenseExampleHeading	<span style="color:#000000;font-family:Times New Roman;font-size:10pt;font-style:italic;font-weight:bold;">Example</span>
Expense Example Narrative [Text Block]	rr_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 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 Portfolio’s operating expenses remain the same. The Example reflects adjustments made to the Portfolio's operating expenses due to the fee waiver agreement with the investment adviser for the first year only. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">PRINCIPAL INVESTMENT STRATEGIES</span>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Investing in multiple investment asset classes, the Portfolio attempts to capitalize on the variation in return potential produced by the interaction of changing financial markets and economic conditions while maintaining a balance over time between investment opportunities and their associated potential risks by following a flexible policy of allocating assets.The Portfolio is tactically and strategically managed to capitalize on changing financial markets and economic conditions following a flexible policy for allocating assets utilizing the following strategic asset class target ranges:Equity and Other* ExposureFixed Income or Debt ExposureCash Equivalents60 – 80%20 – 40%0 – 10%*Other exposure includes REIT and commodity-related investments.These foregoing percentage target ranges are not intended to establish minimum and maximum limits. The adviser may deviate from the asset class target ranges in pursuit of total return and in response to changing market and economic conditions, and, may invest a greater or lesser percentage in any strategic asset class component when the adviser deems it favorable to do so in order to achieve the Portfolio’s investment objective.The Portfolio operates primarily as a “fund of funds” to gain the Portfolio’s multi-asset class exposure. The fund may invest in underlying Portfolios of Northwestern Mutual Series Fund, Inc. (each, an “Underlying Portfolio”) and exchange-traded funds (“ETFs”) which are not portfolios of Northwestern Mutual Series Fund, Inc. The Portfolio may obtain equity exposure by investing in one or more of the domestic or international Underlying Portfolios or ETFs and may obtain fixed income exposure by investing in one or more of the fixed income Underlying Portfolios or ETFs. The cash equivalent portion of the Portfolio may include, but is not limited to, ETFs, investments in debt securities issued or guaranteed by the U.S. government or its agencies or instrumentalities, including mortgage- and asset-backed securities, as well as commercial paper, banker’s acceptances, certificates of deposit and time deposits. In order to enhance short duration returns, the adviser may purchase ultra-short bond ETFs. For purposes of the strategic asset class ranges utilized herein, the adviser includes these instruments in the Cash Equivalents asset class together with cash and cash equivalent instruments. The Portfolio may also invest in ETFs that invest in real estate investment trusts (REITs). The Portfolio may invest in commodities through the purchase of swaps on physical commodities or commodity indices, including those which are traded in over-the-counter markets (“OTC”). The Portfolio may also invest in ETFs for purposes of obtaining exposure to commodities markets. The adviser allocates the Portfolio’s assets among the Underlying Portfolios and ETFs based on the adviser’s economic and market outlook and the investment objectives and strategies of the Underlying Portfolios and ETFs. With respect to the equity and international Underlying Portfolios and ETFs, the adviser considers their investment focus on small, mid or large market capitalizations, domestic or foreign investments, whether the Underlying Portfolio or ETF is diversified or non-diversified and whether it employs a “growth” or “value” style of investing, among other characteristics. With respect to fixed income Underlying Portfolios and ETFs, the adviser considers their focus on investment grade or non-investment grade securities, domestic or foreign investments, whether the issuer is a government or government agency, the duration (that is, a measure of the sensitivity to changes in interest rates) and maturity of the Underlying Portfolio or ETF, and other characteristics. The adviser regularly reviews and adjusts the allocation among the Underlying Portfolios and ETFs to favor investments in those Underlying Portfolios and ETFs that the adviser believes provide the most favorable position for achieving the Portfolio’s investment objective. In connection with the allocation process, the Portfolio may invest more than 25% of its assets in one Underlying Portfolio or one ETF.Through its investments in the equity Underlying Portfolios and ETFs, the Portfolio may be exposed to a wide range of equity securities and other instruments, including small, mid and large cap U.S. and non-U.S. stocks. Equity securities could include common and preferred stocks, securities convertible into stocks and depositary receipts for those securities. Through its investments in the fixed income Underlying Portfolios and ETFs, the Portfolio may be exposed to a wide range of fixed income securities with varying durations and maturities, including investment grade and non-investment grade debt securities, debt of corporate and government issuers, inflation-indexed debt securities, and other fixed income instruments. The Fund considers a fixed income security to be investment grade if the security is rated investment grade by at least two of the three credit rating agencies (BBB- or higher by S&P; Baa3 or higher by Moody’s; BBB- or higher by Fitch) and a security to be non-investment grade if the security is rated below investment grade by at least two of the three credit ratings agencies (BB+ or lower by S&P; Ba1 or lower by Moody’s; BB+ or lower by Fitch). An Underlying Portfolio or ETF may invest a large percentage of its assets in a single issuer, security, market or sector (or a limited group thereof) or in the case of an international Underlying Portfolio or ETF, may invest in emerging markets, a small number of countries or a particular geographic region. An Underlying Portfolio or ETF may also use certain derivative instruments including futures, forwards, options and swaps to meet its investment objective and for cash management purposes.When the adviser deems it to be more efficient or advantageous in managing the Portfolio, the adviser may utilize futures, options, forwards and swap agreements (including the purchase and sale of total return equity swaps and credit default swaps) to gain additional exposure to certain markets, sectors, regions, or commodities, as alternatives to investments in Underlying Portfolios or ETFs, to adjust the Portfolio for the adviser’s view on style or term structure and duration, to provide increased flexibility in asset allocation, to earn income and to otherwise seek to enhance returns or to hedge foreign currency exposure.The Portfolio is designed primarily for investors who want their investment allocated across major asset classes while pursuing the growth potential of equities with a smaller allocation to bonds. The investor should be willing to accept fluctuation in share prices that are typical for a portfolio that holds equity investments.
Risk [Heading]	rr_RiskHeading	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">PRINCIPAL RISKS</span>
Risk [Text Block]	rr_RiskTextBlock	•Commodities Risk – The Portfolio’s investments in ETFs and total return swaps whose performance is linked to the price of an underlying commodity or commodity index may be subject to the risks of investing in physical commodities, including risks posed by regulatory, economic and political developments, weather events, natural disasters and market disruption. Commodity prices may have greater volatility than investments in traditional securities.•Derivatives Risk – The value of a derivative generally depends upon, or is derived from, an underlying asset, reference rate or index. The primary risks associated with the Portfolio’s use of derivatives are the risk that changes in the value of the derivatives may not correlate as intended with the underlying asset, rate or index, the risk of adverse price movements in the market, the risk of missed opportunities in other investments and the risk that the counterparty to a derivatives transaction fails to make the required payment or otherwise comply with the terms of the contract. Certain derivatives involve leverage, which could cause the Portfolio to lose more than the principal amount invested. Other risks include management, interest rate and liquidity risks. The Portfolio’s purchase of forwards and futures contracts may involve risks related to imperfect correlation between the prices of such instruments and the price of the underlying asset, as well as leverage, liquidity and volatility risks. In addition, the purchase of forwards also involves counterparty credit risk as well as heightened market risk. The Portfolio’s purchase of total return equity swap agreements and total return commodities swap agreements may pose risk arising from losses if the underlying reference asset does not perform as anticipated; such agreements are also subject to counterparty credit, liquidity and leveraging risks. The Portfolio’s use of options involve risk related to the direction and timing of market movements in the price of the underlying asset, obligations related to exercise of the option, and potential loss in value of the initial investment.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<span style="color:#000000;font-family:Arial;font-size:10.02pt;font-weight:bold;">PERFORMANCE</span>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The following bar chart illustrates the risks of investing in the Portfolio by showing how the performance of the Portfolio has varied from year to year. The table accompanying the bar chart shows the Portfolio’s average annual total return over certain time periods and compares the Portfolio’s returns with those of a broad measure of market performance for both equity and fixed income securities and the returns of a composite of indices of securities with characteristics similar to those the Portfolio typically holds.Returns are based on past results and are not an indication of future performance.Neither the bar chart nor the table reflects the fees and expenses separately charged by the variable annuity contract or variable life insurance policy separate account that invests in the Portfolio and returns would be lower if those fees and expenses were reflected.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;margin-left:0%;">The following bar chart illustrates the risks of investing in the Portfolio by showing how the performance of the Portfolio has varied </span><span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;">from year to year. The table accompanying the bar chart shows the Portfolio’s average annual total return over certain time periods and compares the Portfolio’s returns with those of a broad measure of market performance for both equity and fixed income securities and the returns of a composite of indices of securities with characteristics similar to those the Portfolio typically holds.</span>
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;">Returns are based on past results and are not an indication of future performance.</span>
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;">Neither the bar chart nor the table reflects the fees and expenses separately charged by the variable annuity contract or variable life insurance policy separate account that invests in the Portfolio and returns would be lower if those fees and expenses were reflected.</span>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Quarter/YearReturnBest Quarter2nd quarter, 202014.30%Worst Quarter1st quarter, 2020-14.95%
Performance Table Heading	rr_PerformanceTableHeading	<span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;font-weight:bold;margin-left:0%;">Average Annual Total Return</span><span style="color:#000000;font-family:Times New Roman;font-size:10.02pt;font-weight:bold;">(for periods ended December 31, 2023)</span>
Asset Allocation Portfolio | Risk Lose Money [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Portfolio shares will rise and fall in value and there is a risk you could lose money by investing in the Portfolio. There can be no assurance that the Portfolio will achieve its objective.
Asset Allocation Portfolio | Active Management Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Active Management Risk – The adviser’s investment strategies and techniques may not perform as expected which could cause the Portfolio to underperform other mutual funds or lose money.
Asset Allocation Portfolio | Affiliated Portfolio Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Affiliated Portfolio Risk – In managing the Portfolio, the adviser has the authority to select, and allocate among, Underlying Portfolios. The adviser may be subject to potential conflicts of interest in selecting Underlying Portfolios because the fees paid to it by some Underlying Portfolios are higher than the fees paid by other Underlying Portfolios. Moreover, a situation could occur where proper action for the Portfolio could be adverse to the interest of the Underlying Portfolios or vice versa.
Asset Allocation Portfolio | Asset Allocation Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Asset Allocation Risk – This Portfolio allocates its investments among multiple investment asset classes and among Underlying Portfolios and ETFs, based upon judgments made by the adviser. The Portfolio could miss attractive investment opportunities by underweighting markets or sectors where there are significant returns, and could lose value by overweighting markets where there are significant declines, or may not correctly predict the times to shift assets from one type of investment to another.
Asset Allocation Portfolio | Convertible Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Convertible Securities Risk – Convertible securities (which can be bonds, notes, debentures, preferred stock, or other securities which are convertible into or exercisable for common stock), are subject to both the credit and interest rate risks associated with fixed income securities and to the stock market risk associated with equity securities. The value of a convertible security may not increase or decrease as rapidly as the underlying common stock. The Portfolio may be forced to convert a security before it would otherwise choose, which may have an adverse effect on the Portfolio’s ability to achieve its investment objective.
Asset Allocation Portfolio | Credit Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Credit Risk – The Portfolio could lose money if the issuer or guarantor of a fixed income security held directly or through an Underlying Portfolio or ETF is unwilling or unable to meet its financial obligations. In addition, changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Portfolio’s investment in that issuer. Changes in credit spreads or improvements in an issuer’s credit quality may increase the risk that an issuer calls outstanding securities prior to their maturity.
Asset Allocation Portfolio | Emerging Markets Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Emerging Markets Risk – Investing in emerging market securities increases foreign investing risk, and may subject the Portfolio to more rapid and extreme changes in the value of its holdings compared with investments made in U.S. securities or in foreign, developed countries. Investments in emerging markets may be subject to political, economic, legal, market, and currency risks. Emerging market securities trade in smaller markets which may experience significant price and market volatility, fluctuations in currency values, interest rates and commodity prices, higher transaction costs, and the increased likelihood of the occurrence of trading difficulties, such as delays in executing, clearing and settling Portfolio transactions or in receiving payment of dividends. Special risks associated with investments in emerging market issuers may include a lack of publicly available information, a lack of uniform disclosure, accounting, financial reporting, and recordkeeping standards, and more limited investor protection provisions when compared with developed economies. Emerging market risks also may include unpredictable and changing political, economic and tax policies, the imposition of capital controls and/or foreign investment limitations by a country, nationalization of businesses, and the imposition of sanctions or restrictions in certain investments by other countries, such as the United States. Investments in Chinese securities may be more vulnerable to political and economic risks than investments in securities from other countries. The Chinese government could, at any time, alter or discontinue the economic reform programs implemented since 1978 which liberalized trade policy and reduced government control.  Changes in these policies could adversely affect Chinese companies or investments in those companies and could substantially affect the value of China’s currency relative to the U.S. dollar. In addition, any public health threat or similar issue could have a significant impact on the Chinese economy, which in turn could adversely affect the Portfolio’s investments.
Asset Allocation Portfolio | Equity Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Equity Securities Risk – The value of equity securities held through the Underlying Portfolios and ETFs, such as common and preferred stocks, could decline if the financial condition of the companies an Underlying Portfolio or ETF is invested in declines or if overall market and economic conditions deteriorate. Equity securities generally have greater price volatility than fixed income securities.
Asset Allocation Portfolio | Exchange Traded Funds Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Exchange Traded Funds Risk – Investing in exchange traded funds (ETFs) may expose the Portfolio to greater risk of loss and price fluctuation than investing directly in a comparable portfolio of stocks comprising the index due to lack of liquidity, the additional expenses incurred as a shareholder in another investment company, and tracking error. ETFs are also subject to the risk that their market prices may trade at a premium or discount to their net asset value, which means the Portfolio will overpay for an ETF’s assets if it is trading at a premium and will get less than the value of the ETF’s assets when selling if it is trading at a discount. An active market for an ETF may not be developed or maintained. Trading of an ETF’s shares may be halted by the exchange, in which case the Portfolio would be unable to sell its ETF shares unless and until trading is resumed. Investing in ultra-short bond ETFs may pose greater risk than investments in cash equivalents such as money market mutual funds, including risks associated with the credit quality, duration and interest rate sensitivity of the bond instruments held within such ETFs. Ultra-short bond ETFs may be more volatile and involve greater credit and interest rate risk than money market funds and other cash equivalents. In addition, the price of an ultra-short bond ETF may fluctuate, while the goal of a money market mutual fund is to maintain its NAV at a stable $1 per share. Ultra-short bond ETFs may lose money despite a stated investment objective of returning capital.
Asset Allocation Portfolio | Foreign Investing Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Foreign Investing Risk – Exposure to investments in foreign securities, including through Underlying Portfolios and ETFs, may subject the Portfolio to more rapid and extreme changes in value or more losses than a fund that invests exclusively in U.S. securities. This risk is due to potentially smaller markets, differing reporting, accounting and auditing standards, and nationalization, expropriation or confiscatory taxation, currency blockage, political and economic conditions, or diplomatic developments. Foreign securities may be adversely affected by decreases in foreign currency values relative to the U.S. dollar and may be less liquid, more volatile, and harder to value than U.S. securities. Exposure to investments in emerging markets heighten these risks due to a lack of established legal, political, business and social frameworks to support securities markets.
Asset Allocation Portfolio | Fund of Funds Investing Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Fund of Funds Investing Risk – The Portfolio’s investment performance is significantly impacted by the investment performance of the Underlying Portfolios and ETFs it holds. The ability of the Portfolio to meet its investment objective is related to the ability of the Underlying Portfolios or ETFs to meet their respective investment objectives as well as the adviser’s allocation decisions with respect to the Underlying Portfolios and ETFs. Each of the Underlying Portfolios and ETFs has its own investment risks, and the Portfolio is indirectly exposed to all the risks of the Underlying Portfolios and ETFs in direct proportion to the amount of assets the Portfolio allocates to each Underlying Portfolio and each ETF. To the extent that the Portfolio invests a significant portion of its assets in a single Underlying Portfolio or ETF, it will be particularly sensitive to the risks associated with that Underlying Portfolio or ETF. Changes in the value of that Underlying Portfolio or ETF may have a significant effect on the Portfolio’s net asset value. The Portfolio will bear a pro rata share of the Underlying Portfolios’ or ETFs’ expenses.
Asset Allocation Portfolio | Geographic Focus Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Geographic Focus Risk – The Portfolio’s performance could be more volatile than that of a more geographically diversified fund and could be significantly impacted as a result of the Portfolio investing a relatively large percentage of its assets in issuers located in a single country, a small number of countries, or a particular geographic region. Also, the Portfolio’s performance may be more closely tied to the market, currency, economic, political, or regulatory conditions in those countries or that region. Similarly, the extent to which an Underlying Portfolio or ETF invests a significant portion of its assets in a single country, a small number of countries or a particular geographic region, may also adversely impact the Portfolio, depending on the Portfolio’s level of investment in that Underlying Portfolio or ETF.
Asset Allocation Portfolio | High Yield Debt Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•High Yield Debt Risk – High yield debt securities (so called “junk bonds”) in which the Portfolio has exposure  have greater interest rate and credit risk, may be more difficult to sell or sell at a reasonable price, have greater risk of loss than higher rated securities, and are predominantly speculative with respect to an issuer’s ability to pay interest and repay principal. In addition, high yield debt securities may be particularly sensitive to changes in the securities markets.
Asset Allocation Portfolio | Interest Rate Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Interest Rate Risk – Prices of fixed income instruments generally rise and fall in response to changes in market interest rates. In a rising interest rate environment, the value of the Portfolio’s fixed income investments to which the Portfolio has exposure is likely to decline. A significant rise in interest rates over a short period of time could cause significant losses in the market value of the Portfolio’s fixed income instruments. Duration measures the price sensitivity of a fixed income instrument to changes in interest rates. The Portfolio’s exposure to fixed income instruments and Underlying Portfolios or ETFs with a longer average portfolio duration will be more sensitive to changes in interest rates than those with a shorter average duration.
Asset Allocation Portfolio | Investment Style Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Investment Style Risk – The Portfolio is subject to risks associated with an Underlying Portfolio’s or ETF's particular style of investing, such as growth or value or a combination of both, and may underperform with respect to its allocation to the Underlying Portfolio or ETF when the market does not favor that particular investment style. Different investment styles tend to shift in and out of favor, depending on market conditions and investor sentiment.
Asset Allocation Portfolio | Large Cap Company Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Large Cap Company Risk – Exposure to investments in large cap stocks could cause the Portfolio to underperform in markets favoring faster growing companies. Large cap stocks tend to be more mature with fewer opportunities to grow and may not have the same growth potential as stocks with smaller capitalizations.
Asset Allocation Portfolio | Large Transaction Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Large Transaction Risk – The Underlying Portfolios are used as investments for certain fund of funds, including the Portfolio, and may have a large percentage of their shares owned by such funds. Large redemption activity by the Portfolio or another fund of funds could result in the Underlying Portfolio being forced to sell portfolio securities at a loss to meet redemptions. The adviser may coordinate directly with the portfolio managers of the Underlying Portfolios to attempt to ensure that transactions are accommodated efficiently, including possibly implementing trades over a period of days rather than all at once. These practices may temporarily affect the adviser’s ability to fully implement the Portfolio’s investment strategies.
Asset Allocation Portfolio | Liquidity Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Liquidity Risk – Particular investments, such as small and micro cap stocks, fixed income securities, foreign securities, in particular emerging markets securities, and derivatives to which the Portfolio has exposure, can be difficult to purchase or sell at an advantageous time or price, if at all. These risks may be magnified during periods of economic turmoil or in an extended economic downturn.
Asset Allocation Portfolio | Market Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Market Risk – The risk that the market price of securities owned by the Portfolio or an Underlying Portfolio or ETF in which the Portfolio invests may go up or down, sometimes rapidly or unpredictably. The value of a security may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Global economies and financial markets are increasingly interconnected, which magnifies the potential that conditions in one country or region might adversely impact issuers in, or foreign exchange rates with, a different country or region. Geopolitical and other events, including war, terrorism, economic uncertainty, trade disputes, public health crises (such as epidemics and pandemics), and related events have led, and in the future may lead, to increased market volatility, which may disrupt U.S. and world economies and markets and may have significant adverse direct or indirect effects on the Portfolio and its investments.
Asset Allocation Portfolio | Micro Cap Company Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Micro Cap Company Risk – Exposure to investments in micro cap stocks may cause the Portfolio to experience more rapid and extreme changes in value than a fund that invests solely in small, mid and large cap stocks due to a more limited track record, narrower product markets, more limited resources, higher risk of failure, and less liquid trading markets.
Asset Allocation Portfolio | Mortgage-and Asset-Backed Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Mortgage- and Asset-Backed Securities Risk – The risks of investing in mortgage-related and other asset-backed securities, including interest rate risk, credit risk, liquidity risk, extension risk and prepayment risk. Mortgage-related and other asset-backed securities represent interests in pools of mortgages or other assets and often involve risks that are different or possibly more acute than risks associated with other types of debt instruments. The value of some mortgage- or asset-backed securities may be particularly sensitive to changes in prevailing interest rates.
Asset Allocation Portfolio | Preferred Stocks Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Preferred Stocks Risk – Preferred stocks often lack a fixed maturity or redemption date and are therefore more susceptible to price fluctuations when interest rates change. They also carry a greater risk of non-receipt of income because unlike interest on debt securities, dividends on preferred stocks must be declared by the issuer’s board of directors before becoming payable.
Asset Allocation Portfolio | REITs Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•REITs Risk – Investments in REITs are subject to the types of risks associated with investing in the real estate industry, including, among other risks: adverse developments affecting the real estate industry; declines in real property values; changes in interest rates; defaults by mortgagors or other borrowers and tenants; lack of availability of mortgage funds or financing; extended vacancies of properties, especially during economic downturns; casualty or condemnation losses; property taxes and operating losses; and governmental actions, such as changes to tax laws, zoning regulations or environmental regulations. REITs are dependent upon the quality of their management, may have limited financial resources and heavy cash flow dependency, may not be diversified geographically or by property type, and may be subject to self-liquidation.
Asset Allocation Portfolio | Sector Focus Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Sector Focus Risk – To the extent the Portfolio invests in Underlying Portfolios or ETFs with a relatively high percentage of its assets in a particular sector, it will have greater exposure to the risks associated with that sector, including the risk that the securities of companies within the sector will underperform due to adverse economic conditions, regulatory or legislative changes, or increased competition affecting the sector. To the extent the Portfolio invests in Underlying Portfolios or ETFs that are underweight in other sectors, the Portfolio risks missing out on advances in those sectors.
Asset Allocation Portfolio | Small and Mid Cap Company Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Small and Mid Cap Company Risk – Exposure to investments in small and mid cap stocks may cause greater risk of loss and price fluctuation than investing in stocks of larger cap companies due to a more limited track record, narrower product markets, more limited resources and less liquid trading markets. These stocks may be more volatile and more difficult to buy and sell than stocks with larger capitalizations.
Asset Allocation Portfolio | U.S. Government Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•U.S. Government Securities Risk – Not all obligations of the U.S. government, its agencies and instrumentalities are backed by the full faith and credit of the U.S. Treasury. Some obligations are backed only by the credit of the issuing agency or instrumentality, and in some cases there may be some risk of default by the issuer. Any guarantee by the U.S. government or its agencies or instrumentalities of a security held by the Portfolio does not apply to the market value of such security or to shares of the Portfolio itself.
Asset Allocation Portfolio | Asset Allocation Portolio
Risk Return Abstract	rr_RiskReturnAbstract
Shareholder Fees(fees paid directly from your investment)	rr_ShareholderFeeOther
Management Fee	rr_ManagementFeesOverAssets	0.53%
Distribution and Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.05%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.43%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.01%	[1]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.43%)	[2]
Total Annual Portfolio Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	0.58%	[1],[2]
1 Year	rr_ExpenseExampleYear01	$ 59
3 Years	rr_ExpenseExampleYear03	279
5 Years	rr_ExpenseExampleYear05	516
10 Years	rr_ExpenseExampleYear10	$ 1,197
2014	rr_AnnualReturn2014	5.15%
2015	rr_AnnualReturn2015	(0.43%)
2016	rr_AnnualReturn2016	7.79%
2017	rr_AnnualReturn2017	14.87%
2018	rr_AnnualReturn2018	(4.88%)
2019	rr_AnnualReturn2019	21.08%
2020	rr_AnnualReturn2020	13.43%
2021	rr_AnnualReturn2021	10.45%
2022	rr_AnnualReturn2022	(14.83%)
2023	rr_AnnualReturn2023	15.24%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	<span style="color:#000000;font-family:Times New Roman;font-size:9.02pt;margin-left:0.0pt;">Best Quarter</span>
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2020
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	14.30%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	<span style="color:#000000;font-family:Times New Roman;font-size:9.02pt;margin-left:0.0pt;">Worst Quarter</span>
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2020
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(14.95%)
1 Yr	rr_AverageAnnualReturnYear01	15.24%
5 Yr	rr_AverageAnnualReturnYear05	8.28%
10 Yr	rr_AverageAnnualReturnYear10	6.26%
Asset Allocation Portfolio | S&P 500® Index(reflects no deduction for fees, expenses or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Yr	rr_AverageAnnualReturnYear01	26.29%
5 Yr	rr_AverageAnnualReturnYear05	15.70%
10 Yr	rr_AverageAnnualReturnYear10	12.03%
Asset Allocation Portfolio | Bloomberg® U.S. Aggregate Bond Index(reflects no deduction for fees, expenses or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Yr	rr_AverageAnnualReturnYear01	5.53%
5 Yr	rr_AverageAnnualReturnYear05	1.10%
10 Yr	rr_AverageAnnualReturnYear10	1.81%
Asset Allocation Portfolio | Asset Allocation Portfolio Blended Composite Benchmark S&P 500® Index (28%), S&P 400® MidCap Index (7%), S&P SmallCap 600 Index (3%), MSCI® EAFE Index (15%), MSCI® Emerging Markets Index (6%), Dow Jones U.S. Select REIT Index (4%), Bloomberg® Commodity IndexSM (5%), Bloomberg® Barclays U.S. Aggregate Bond Index (30%) and ICE BofA® US 3-Month Treasury Bill Index (2%) (reflects no deduction for fees, expenses or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Yr	rr_AverageAnnualReturnYear01	16.69%	[3]
5 Yr	rr_AverageAnnualReturnYear05	9.25%	[3]
10 Yr	rr_AverageAnnualReturnYear10	7.06%	[3]

[1] Includes fees and expenses incurred indirectly by the Portfolio as a result of investments in other investment companies (Acquired Fund Fees and Expenses). The operating expenses of the Portfolio reflected in the Portfolio's most recent annual report and Financial Highlights do not include the Acquired Fund Fees and Expenses.

[2] The Portfolio's investment adviser has entered into a written agreement to waive a portion of its management fee. This fee waiver agreement may be terminated by the adviser at any time after April 30, 2025.

[3] Effective May 1, 2024, the Portfolio modified the constituent components of the Asset Allocation Portfolio Blended Composite Benchmark (the “Composite Benchmark”) and changed the target weightings across the Composite Benchmark components. As of such date, the Composite Benchmark was modified to (i) delete the high yield component and add real estate and commodities components; and (ii) replace Russell® Indices with S&P® Indices for each of the three domestic equity Composite Benchmark components. Performance of the Portfolio for periods prior to May 1, 2024, are relative to the updated Composite Benchmark.