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Risk Return Abstract rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName EQ ADVISORS TRUST
Prospectus Date rr_ProspectusDate May 01, 2025
Target 2035 Allocation Portfolio  
Risk Return Abstract rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading <span style="color:#000000;font-family:Arial;font-size:11pt;font-weight:bold;">Target 2035 Allocation Portfolio</span><span style="color:#000000;font-family:Arial;font-size:11pt;font-weight:bold;line-height:13pt;">  </span><span style="color:#000000;font-family:Arial;font-size:11pt;font-weight:bold;">— Class IB and Class K Shares</span>
Objective [Heading] rr_ObjectiveHeading <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Investment Objective:</span>
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock Seeks the highest total return over time consistent with its asset mix. Total return includes capital growth and income.
Expense [Heading] rr_ExpenseHeading <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;text-transform:uppercase;">Fees and Expenses of the Portfolio</span>
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Portfolio. The table below does not reflect any fees and expenses associated with variable life insurance contracts and variable annuity certificates and contracts (“Contracts”), which would increase overall fees and expenses. See the Contract prospectus for a description of those fees and expenses.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Shareholder Fees</span> <br/><span style="color:#000000;font-family:Arial;font-size:10pt;">(fees paid directly from your investment)</span>
Operating Expenses Caption [Text] rr_OperatingExpensesCaption <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Annual Portfolio Operating Expenses</span><span style="color:#000000;font-family:Arial;font-size:10pt;">(expenses that you pay each year as a percentage of the value of your investment)</span>
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;text-transform:uppercase;">Portfolio Turnover</span>
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Portfolio will not incur transaction costs, such as commissions, when it buys and sells shares of the Underlying Portfolios (or “turns over” its portfolio), but it could incur transaction costs if it were to buy and sell other types of securities directly. If the Portfolio were to buy and sell other types of securities directly, a higher portfolio turnover rate could indicate higher transaction costs. Such costs, if incurred, would not be reflected in annual fund operating expenses or in the example, and would affect the Portfolio’s performance. During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 13% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 13.00%
Expense Example [Heading] rr_ExpenseExampleHeading <span style="color:#000000;font-family:Arial;font-size:10pt;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 portfolios. The example assumes that you invest $10,000 in the Portfolio for the periods indicated, that your investment has a 5% return each year, and that the Portfolio’s operating expenses remain the same. This example does not reflect any Contract-related fees and expenses, including redemption fees (if any) at the Contract level. If such fees and expenses were reflected, the total expenses would be higher. Although your actual costs may be higher or lower, based on these assumptions, whether you redeem or hold your shares, your costs would be:
Strategy [Heading] rr_StrategyHeading <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;text-transform:uppercase;">Investments, Risks, and Performance</span><span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Investment Strategy</span>
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock The Portfolio is managed by Equitable Investment Management Group, LLC (“EIM” or “Adviser”). The Portfolio seeks to achieve its objective by investing in other mutual funds (the “Underlying Portfolios”) managed by the Adviser or Equitable Investment Management, LLC, an affiliate of the Adviser, and sub-advised by one or more investment sub-advisers, which represent a variety of asset classes and investment styles. The Portfolio is managed based on the specific retirement (or target) year included in its name (2035) and assumes that an investor retires at age 65; however, the Portfolio should not be selected solely on the basis of the target year or an investor’s age. The Portfolio’s asset mix will become more conservative each year until reaching the year approximately 10 years after the retirement year at which time it is intended that the asset mix will become relatively stable. The Portfolio is designed to balance the need for appreciation with the need for income as retirement approaches and to support an income stream over a long-term retirement withdrawal horizon. The Portfolio is not designed for a lump sum redemption at the target year and does not guarantee a particular level of income. The Portfolio maintains significant allocations to equities both prior to and after the target year and is generally expected to reach its most conservative allocation 10 years after the target year. The asset classes in which the Portfolio may invest generally are divided into domestic equity securities (such as the common stock of U.S. companies of any size), international equity securities (such as the common stock of foreign companies of any size, including those located in developed and emerging markets) and fixed income investments (such as debt securities issued by the U.S. Government and its agencies and instrumentalities, mortgage- and asset-backed securities (primarily government, corporate, and investment grade agency mortgage- and asset-backed securities), domestic and foreign investment grade bonds and high yield (or “junk”) bonds, and short-term investments such as money market instruments). The Portfolio is not limited with respect to the maturity, duration or credit quality of the fixed income securities in which it invests. The Underlying Portfolios in which the Portfolio may invest also may invest in companies of any size and may invest in fixed income securities of any maturity, duration or credit quality. The longer a security’s duration, the more sensitive it will be to changes in interest rates, which may increase the volatility of the security’s value and may lead to losses. The Portfolio may hold cash or invest in short-term paper and other short-term investments (instead of allocating investments to an Underlying Portfolio) as deemed appropriate by the Adviser. The Portfolio may invest in Underlying Portfolios that employ derivatives (including futures contracts) for a variety of purposes, including to reduce risk, to seek enhanced returns from certain asset classes, and to leverage exposure to certain asset classes. The following chart shows the Portfolio’s target allocation for the various asset classes (as represented by the holdings of the Underlying Portfolios in which the Portfolio invests) as of the date of this Prospectus.Approximate Number of Years Before/After Retirement Year10 YearsBefore5 YearsBeforeRetirement5 YearsAfter10 YearsAfterAsset ClassDomestic Equity50%42%35%30%15%International Equity20%18%15%10%5%Fixed Income30%40%50%60%80%The following chart shows the Portfolio’s “glide path” and illustrates how the asset mix of the Portfolio will change over time. In general, the asset mix of the Portfolio will gradually shift from one comprised largely of Underlying Portfolios that emphasize investments in stocks to one that increasingly favors Underlying Portfolios that emphasize investments in bonds and money market instruments. The asset mix of the Portfolio will become more conservative each year until reaching the year approximately 10 years after the retirement year, at which time the asset mix will become relatively stable.As of December 31, 2024, the Portfolio’s asset mix was allocated approximately 50.7% to domestic equity, 21.4% to international equity, and 27.9% to fixed income. The Portfolio’s annual and semi-annual financial statements filed on Form N-CSR set forth the actual allocations to the Underlying Portfolios as of the dates of the financial statements. The Adviser establishes the asset mix of the Portfolio and selects the specific Underlying Portfolios in which to invest using its proprietary investment process, which is based on a variety of factors that include fundamental research regarding the investment characteristics of each asset class and the Underlying Portfolios (such as risk, volatility, and the potential for growth and income), as well as its outlook for the economy and financial markets. The Adviser may change the asset allocation targets and may add new Underlying Portfolios or replace or eliminate existing Underlying Portfolios without notice or shareholder approval. The Adviser may sell the Portfolio’s holdings for a variety of reasons, including to invest in an Underlying Portfolio that the Adviser believes offers superior investment opportunities. The Adviser will permit the relative weightings of the Portfolio’s asset classes to vary in response to the markets, ordinarily by not more than plus/minus 15%. Beyond those ranges, the Adviser generally will use cash flows, and periodically will rebalance the Portfolio’s investments, to keep the Portfolio within its asset allocation targets. However, there may be occasions when those ranges will expand to 20% due to a variety of factors, including appreciation or depreciation of one or more of the asset classes. The Portfolio will purchase Class K shares or Class I shares, as applicable, of the Underlying Portfolios, which are not subject to distribution or service (Rule 12b-1) fees.
Risk [Heading] rr_RiskHeading <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Risks</span>
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Risk/Return Bar Chart and Table</span>
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The bar chart and table below provide some indication of the risks of investing in the Portfolio by showing changes in the Portfolio’s performance from year to year and by showing how the Portfolio’s average annual total returns for the past one, five and ten years through December 31, 2024, compared to the returns of a broad-based securities market index.The additional securities market index shows how the Portfolio's performance compared with the returns of another index that has characteristics relevant to the Portfolio's investment strategies.Past performance is not an indication of future performance.For periods prior to November 13, 2023, the performance shown below is that of the Portfolio's predecessor, which was managed by the Adviser and had a substantially identical investment objective, policies and strategies as the Portfolio.  The performance results do not reflect any Contract-related fees and expenses, which would reduce the performance results.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns <span style="font-family:Arial;font-size:10pt;margin-left:0%;">The bar chart and table below provide some indication of the risks of investing in the Portfolio by showing changes in the Portfolio’s performance from year to year and by showing how the Portfolio’s average annual total returns for the past one, five and ten years through December 31, </span><span style="font-family:Arial;font-size:10pt;">2024, compared to the returns of a broad-based securities market index.</span>
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex <span style="font-family:Arial;font-size:10pt;">The additional securities market </span><span style="font-family:Arial;font-size:10pt;margin-left:0%;">index shows how the Portfolio's performance compared with the returns of another index that has characteristics relevant to the </span><span style="font-family:Arial;font-size:10pt;">Portfolio's investment strategies.</span>
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture <span style="font-family:Arial;font-size:10pt;">Past performance is not an indication of future performance.</span>
Bar Chart [Heading] rr_BarChartHeading <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Calendar Year Annual Total Returns — Class IB</span>
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads <span style="color:#000000;font-family:Arial;font-size:10pt;">The performance results do not reflect any Contract-related fees and expenses, which would reduce the performance results.</span>
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best quarter (% and time period)16.05%2020 2nd QuarterWorst quarter (% and time period)-17.89%2020 1st Quarter
Performance Table Heading rr_PerformanceTableHeading <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Average Annual Total Returns</span>
Target 2035 Allocation Portfolio | Risk Lose Money [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock The value of your investment may fall, sometimes sharply, and you could lose money by investing in the Portfolio.
Target 2035 Allocation Portfolio | Risk Not Insured Depository Institution [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock An investment in the Portfolio is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Target 2035 Allocation Portfolio | Market Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Market Risk —  The Portfolio is subject to the risk that the securities markets will move down, sometimes rapidly and unpredictably, based on overall economic conditions and other factors, which may negatively affect Portfolio performance. Securities markets also may experience long periods of decline in value. The value of a security can be more volatile than the market as a whole and can perform differently from the market as a whole. Any issuer of securities may perform poorly, causing the value of its securities to decline. Poor performance may be caused by a variety of factors, such as poor management decisions; reduced demand for the issuer’s goods or services; competitive pressures; negative perception in the marketplace; loss of major customers; strategic initiatives such as mergers or acquisitions and the market response to any such initiatives; and the historical and prospective earnings of the issuer. The value of a security also may decline due to general market conditions, such as real or perceived adverse economic or political conditions, inflation rates and/or investor expectations concerning such rates, changes in interest rates, recessions, or adverse investor sentiment generally. During a general downturn in the securities markets, multiple asset classes may decline in value simultaneously. Even when securities markets perform well, there can be no assurance that the investments held by the Portfolio will increase in value along with the broader market. Changes in the financial condition of (or other event affecting) a single issuer can impact an individual sector or industry, or the securities markets as a whole. The value of a security also may decline due to factors that affect a particular sector or industry, such as tariffs, labor shortages, or increased production costs and competitive conditions within the sector or industry. Geopolitical events, including acts of terrorism, tensions, war or other open conflicts between nations, or political or economic dysfunction within nations that are global economic powers or major oil or other commodities producers, may lead to overall instability in world economies and markets generally and have led, and may in the future lead, to increased market volatility and may have adverse long-term effects. World markets, or those in a particular region, may all react in similar fashion to economic, political or other developments. Events such as environmental and natural disasters or other catastrophes, public health crises (such as epidemics and pandemics), social unrest, and cybersecurity incidents, and governments’ reactions (or failure to react) to such events, could cause uncertainty in the markets and may adversely affect the performance of the global economy. Impacts from climate change may include significant risks to global financial assets and economic growth. The extent and duration of such events and resulting market disruptions could be substantial and could magnify the impact of other risks to the Portfolio. The value and liquidity of the Portfolio’s investments may be negatively affected by developments in other countries and regions, whether or not the Portfolio invests in securities of issuers located in or with significant exposure to the countries or regions directly affected. Changes in government or central bank policies, changes in existing laws and regulations, and political, diplomatic and other events within the United States and abroad could cause uncertainty in the markets, may affect investor and consumer confidence, and may adversely impact financial markets and the broader economy, perhaps suddenly and to a significant degree. High public debt and deficits in the United States and other countries create ongoing systemic and market risks and policymaking uncertainty and may negatively affect economic conditions and the values of markets, sectors and companies in which the Portfolio invests. In addition, markets and market participants are increasingly reliant on information data systems. Inaccurate data, software or other technology malfunctions, programming inaccuracies, unauthorized use or access, and similar circumstances may impair the performance of these systems and may have an adverse impact upon a single issuer, a group of issuers, or the market at large. Furthermore, impacts from the rapidly growing use of artificial intelligence technologies, including by market participants, may include significant risks to global financial markets.
Target 2035 Allocation Portfolio | Asset Allocation Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Asset Allocation Risk —  The Portfolio’s investment performance depends upon how its assets are allocated across various asset classes and how its assets are invested within those asset classes. Some asset classes and investments may perform below expectations, or below the securities markets generally, over short and extended periods. The allocation strategies used and the allocation and investment decisions made could cause the Portfolio to lose value and may not produce the desired results.
Target 2035 Allocation Portfolio | Equity Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Equity Risk —  In general, the values of stocks and other equity securities fluctuate, and sometimes widely fluctuate, in response to changes in a company’s financial condition as well as general market, economic and political conditions and other factors. Stock markets tend to run in cycles, with periods when stock prices generally go up and periods when stock prices generally go down. However, stock markets also can move up and down rapidly and unpredictably. In addition, common stock prices may be particularly sensitive to rising interest rates, which increase borrowing costs and the costs of capital. The Portfolio may experience a significant or complete loss on its investment in an equity security.
Target 2035 Allocation Portfolio | Interest Rate Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Interest Rate Risk —  Changes in interest rates may affect the yield, liquidity and value of investments in debt securities or other income-producing securities. Changes in interest rates also may affect the value of other securities. When interest rates rise, the value of the Portfolio’s debt securities generally declines. Conversely, when interest rates decline, the value of the Portfolio’s debt securities generally rises. Typically, the longer the maturity (i.e., the term of a debt security) or duration (i.e., a measure of the sensitivity of a debt security to changes in market interest rates, based on the entire cash flow associated with the security) of a debt security, the greater the effect a change in interest rates could have on the security’s price. Thus, the sensitivity of the Portfolio’s debt securities to interest rate risk will increase the greater the duration of those securities. Changes in government or central bank monetary policy may have a substantial and immediate impact on interest rates, which could result in losses to the Portfolio.
Target 2035 Allocation Portfolio | Credit Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Credit Risk —  The Portfolio is subject to the risk that the issuer or guarantor of a fixed income security, or the counterparty to a transaction, is unable or unwilling, or is perceived as unable or unwilling, to make timely interest or principal payments or otherwise honor its obligations, or defaults completely, which may cause the Portfolio’s holdings to lose value. The downgrade of a security’s credit rating may decrease its value. Lower credit quality also may lead to greater volatility in the price of a security and may negatively affect a security’s liquidity. The credit quality of a security can deteriorate suddenly and rapidly. The Portfolio may experience a significant or complete loss on a fixed income security or a transaction.
Target 2035 Allocation Portfolio | Target Date Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Target Date Risk —  The Portfolio does not provide guaranteed income or payouts to an investor at or after the target year. An investment in the Portfolio may decline in value and will not ensure that an investor will have assets sufficient to cover retirement expenses or that an investor will have enough saved to be able to retire in, or within a few years of, the target year identified in the Portfolio’s name. The adequacy of an investor’s account at and after the target year will depend on a variety of factors, including the amount of money invested in the Portfolio, the length of time the investment was held, and the Portfolio’s returns over time.
Target 2035 Allocation Portfolio | Risks Related to Investments in Underlying Portfolios [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Risks Related to Investments in Underlying Portfolios —  When the Portfolio invests in an Underlying Portfolio, it will indirectly bear its proportionate share of the fees and expenses incurred by the Underlying Portfolio. These fees and expenses are in addition to the advisory fees and other expenses that the Portfolio and its shareholders bear directly in connection with the Portfolio’s own operations. As a result, the Portfolio’s shareholders will be subject to two layers of fees and expenses with respect to investments in the Portfolio. The cost of investing in the Portfolio, therefore, may be higher than the cost of investing in a mutual fund that invests directly in individual stocks and bonds. The Portfolio’s performance depends upon a favorable allocation by the Adviser among the Underlying Portfolios, as well as the ability of the Underlying Portfolios to generate favorable performance. The Underlying Portfolios’ investment programs may not be complementary, which could adversely affect the Portfolio’s performance. The Portfolio’s net asset value is subject to fluctuations in the net asset values of the Underlying Portfolios in which it invests. The Portfolio is also subject to the risks associated with the securities or other investments in which the Underlying Portfolios invest, and the ability of the Portfolio to meet its investment objective will directly depend on the ability of the Underlying Portfolios to meet their respective investment objectives. The Portfolio and the Underlying Portfolios are subject to certain general investment risks, including market risk, asset class risk, issuer-specific risk, investment style risk, portfolio management risk, and regulatory risk. In addition, to the extent the Portfolio invests in Underlying Portfolios that invest in equity securities, fixed income securities, and/or foreign securities, the Portfolio is subject to the risks associated with investing in such securities. The extent to which the investment performance and risks associated with the Portfolio correlate to those of a particular Underlying Portfolio will depend upon the extent to which the Portfolio’s assets are allocated from time to time for investment in the Underlying Portfolio, which will vary.
Target 2035 Allocation Portfolio | Affiliated Portfolio Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Affiliated Portfolio Risk —  The Adviser is subject to conflicts of interest in selecting, and allocating the Portfolio’s assets among, the various Underlying Portfolios because the revenue and/or profits the Adviser and its affiliates receive from some of the Underlying Portfolios is higher than the revenue and/or profits received from other Underlying Portfolios for the services the Adviser and its affiliates provide. The Portfolio invests in affiliated Underlying Portfolios; unaffiliated Underlying Portfolios generally are not considered for investment.
Target 2035 Allocation Portfolio | Derivatives Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Derivatives Risk —  The Portfolio’s investments in derivatives may rise or fall in value more rapidly than other investments and may reduce the Portfolio’s returns and increase the volatility of the Portfolio’s net asset value. Investing in derivatives involves investment techniques and risk analyses different from, and risks in some respects greater than, those associated with investing in more traditional investments, such as stocks and bonds. Derivatives may be leveraged such that a small investment can have a significant impact on the Portfolio’s exposure to stock market values, interest rates, or other investments. As a result, a relatively small price movement in a derivatives contract may cause an immediate and substantial loss, and the Portfolio could lose more than the amount it invested. Some derivatives can have the potential for unlimited losses. In addition, it may be difficult or impossible for the Portfolio to purchase or sell certain derivatives in sufficient amounts to achieve the desired level of exposure, or to terminate or offset existing arrangements, which may result in a loss or may be costly to the Portfolio. Some derivatives are more sensitive to market price fluctuations and to interest rate changes than other investments. Derivatives may not behave as anticipated by the Portfolio, and derivatives strategies that are successful under certain market conditions may be less successful or unsuccessful under other market conditions. The Portfolio also may be exposed to losses if the counterparty in the transaction is unable or unwilling to fulfill its contractual obligation. In certain cases, the Portfolio may be hindered or delayed in exercising remedies against or closing out derivatives with a counterparty, resulting in additional losses. Derivatives also may be subject to the risk of mispricing or improper valuation, and valuation may be more difficult in times of market turmoil. Changes to the regulation of derivatives markets and mutual funds’ use of derivatives may impact the Portfolio’s ability to maintain its investments in derivatives, make derivatives more costly, limit their availability, adversely affect their value or performance, or otherwise disrupt markets.
Target 2035 Allocation Portfolio | Foreign Securities Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Foreign Securities Risk —  Investments in foreign securities involve risks in addition to those associated with investments in U.S. securities. Foreign markets may be less liquid, more volatile and subject to less government supervision and regulation than U.S. markets, and it may take more time to clear and settle trades involving foreign securities, which could negatively impact the Portfolio’s investments and cause it to lose money. Security values also may be negatively affected by changes in the exchange rates between the U.S. dollar and foreign currencies. Differences between U.S. and foreign legal, political and economic systems, regulatory regimes and market practices, as well as changes in international trading patterns, trade barriers and other protectionist trade policies (including those of the United States), tariffs, governmental instability, acts of terrorism, war or other open conflicts, or other political, diplomatic or economic actions, also may adversely impact security values. Foreign securities are also subject to the risks associated with the potential imposition of economic or other sanctions against a particular foreign country, its nationals, businesses or industries. World markets, or those in a particular region, may all react in similar fashion to economic, political or other developments. Events and evolving conditions in certain economies or markets may alter the risks associated with investments tied to countries or regions that historically were perceived as comparatively stable and make such investments riskier and more volatile. Regardless of where a company is organized or its stock is traded, its performance may be significantly affected by events in regions from which it derives its profits or in which it conducts significant operations.
Target 2035 Allocation Portfolio | Currency Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Currency Risk —  Investments that are denominated in or that provide exposure to foreign currencies are subject to the risk that those currencies will decline in value relative to the U.S. dollar. Any such decline may erode or reverse any potential gains from an investment in securities denominated in foreign currency or may widen existing loss. In the case of hedging positions, there is the risk that the U.S. dollar will decline in value relative to the currency being hedged. Currency rates may fluctuate significantly over short periods of time.
Target 2035 Allocation Portfolio | European Economic Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock European Economic Risk —  The economies of European Union (“EU”) member countries and their trading partners, as well as the broader global economy, may be adversely affected by changes in the euro’s exchange rate, changes in EU or governmental regulations on trade, geopolitical and other events, including acts of terrorism, tensions, war or other open conflicts, and the threat of default or an actual default by an EU member country on its sovereign debt, which could negatively impact the Portfolio’s investments and cause it to lose money. Events in Europe may continue to impact the economies of every European country and their economic partners. The ongoing Russia-Ukraine conflict, the resulting responses by the United States and other countries, and the potential for wider conflict have had, and could continue to have, severe adverse effects on regional and global economies and could further increase volatility and uncertainty in the financial markets. In addition, uncertainties regarding the viability of the EU have impacted and may continue to impact regional and global markets. There are ongoing concerns regarding the economies of certain European countries and/or their sovereign debt following the United Kingdom’s withdrawal from the EU, commonly referred to as “Brexit”. Any further withdrawals from the EU could cause significant regional and global market disruption, which may negatively impact the Portfolio’s investments and cause it to lose money. Furthermore, the national politics of European countries have been unpredictable; unanticipated or sudden political or social developments may result in sudden and significant investment losses.
Target 2035 Allocation Portfolio | Futures Contract Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Futures Contract Risk —  The primary risks associated with the use of futures contracts are (a) the imperfect correlation between the change in market value of the instruments held by the Portfolio and the price of the futures contract; (b) liquidity risks, including the possible absence of a liquid secondary market for a futures contract and the resulting inability to close a futures contract when desired; (c) losses (potentially unlimited) caused by unanticipated market movements; (d) an investment manager’s inability to predict correctly the direction of securities prices, interest rates, currency exchange rates and other economic factors; (e) the possibility that a counterparty, clearing member or clearinghouse will default in the performance of its obligations; (f) if the Portfolio has insufficient cash, it may have to sell securities from its portfolio to meet daily variation margin requirements, and the Portfolio may have to sell securities at a time when it may be disadvantageous to do so; and (g) transaction costs associated with investments in futures contracts may be significant, which could cause or increase losses or reduce gains. Futures contracts are also subject to the same risks as the underlying investments to which they provide exposure. In addition, futures contracts may subject the Portfolio to leveraging risk.
Target 2035 Allocation Portfolio | Investment Grade Securities Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Investment Grade Securities Risk —  Securities rated in the lower investment grade rating categories (e.g., BBB or Baa) are considered investment grade securities, but may have more risk than higher rated obligations because they are regarded as having only an adequate capacity to pay principal and interest, are considered to lack outstanding investment characteristics, and may possess certain speculative characteristics.
Target 2035 Allocation Portfolio | Large-Cap Company Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Large-Cap Company Risk —  Larger more established companies may be unable to respond quickly to new competitive challenges such as changes in technology and consumer tastes, which may lead to a decline in their market price. Many larger companies also may not be able to attain the high growth rate of successful smaller companies, especially during extended periods of economic expansion.
Target 2035 Allocation Portfolio | Leveraging Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Leveraging Risk —  When the Portfolio leverages its holdings, the value of an investment in the Portfolio will be more volatile and all other risks will tend to be compounded. Investments that create leverage can result in losses to the Portfolio that exceed the amount originally invested and may accelerate the rate of losses (some of which may be sudden or substantial). For certain investments that create leverage, relatively small market fluctuations can result in large changes in the value of such investments. There can be no assurance that the Portfolio’s use of any leverage will be successful.
Target 2035 Allocation Portfolio | Liquidity Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Liquidity Risk —  From time to time, there may be little or no active trading market for a particular investment in which the Portfolio may invest or is invested. In such a market, the value of such an investment and the Portfolio’s share price may fall dramatically. Illiquid investments may be difficult or impossible to sell or purchase at an advantageous time or price or in sufficient amounts to achieve the Portfolio’s desired level of exposure. To meet redemption requests during periods of illiquidity, the Portfolio may be forced to dispose of investments at unfavorable times or prices and/or under unfavorable conditions, which may result in losses or may be costly to the Portfolio. Investments that are illiquid or that trade in lower volumes may be more difficult to value. The Portfolio also may not receive its proceeds from the sale of certain investments for an extended period of time. Certain investments that were liquid when purchased may later become illiquid, sometimes abruptly, particularly in times of overall economic distress or adverse investor perception. An inability to sell a portfolio position can adversely affect the Portfolio’s value or prevent the Portfolio from being able to take advantage of other investment opportunities. During periods of market stress, an investment or even an entire market segment may become illiquid, sometimes abruptly, which can adversely affect the Portfolio’s ability to limit losses. In addition, a reduction in the ability or willingness of dealers and other institutional investors to make a market in certain securities may result in decreased liquidity in certain markets.
Target 2035 Allocation Portfolio | Mid-Cap and Small-Cap Company Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Mid-Cap and Small-Cap Company Risk —  Mid-cap and small-cap companies carry additional risks because the operating histories of these companies tend to be more limited, their earnings and revenues less predictable (and some companies may be experiencing significant losses), and their share prices more volatile than those of larger, more established companies, all of which can negatively affect their value. In general, these risks are greater for small-cap companies than for mid-cap companies.
Target 2035 Allocation Portfolio | Mortgage-Related and Other Asset-Backed Securities Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Mortgage-Related and Other Asset-Backed Securities Risk —  Declines in the credit quality of and defaults by the issuers of mortgage-related and other asset-backed securities or instability in the markets for such securities may decrease the value of such securities, which could result in losses to the Portfolio, and may reduce the liquidity of such securities and make such securities more difficult to purchase or sell at an advantageous time and price. In addition, borrowers may default on the obligations that underlie mortgage-related and other asset-backed securities. The risk of defaults by borrowers generally is greater during times of rising interest rates and/or unemployment rates. The impairment (or loss) of the value of collateral or other assets underlying mortgage-related and other asset-backed securities will result in a reduction in the value of the securities. Certain collateral may be difficult to locate in the event of default, or may be lost, and recoveries of depreciated or damaged collateral may not fully cover payments due on such collateral. Asset-backed securities may not have the benefit of a security interest in collateral comparable to that of mortgage assets, resulting in additional credit risk. Furthermore, mortgage-related and other asset-backed securities typically provide the issuer with the right to prepay the security prior to maturity. During periods of rising interest rates, the rate of prepayments tends to decrease because borrowers are less likely to prepay debt (such as mortgage debt or automobile loans). Slower than expected payments can extend the average lives of mortgage-related and other asset-backed securities, and this may “lock in” a below market interest rate and increase the security’s duration and interest rate sensitivity, which may increase the volatility of the security’s value and may lead to losses. During periods of falling interest rates, the rate of prepayments tends to increase because borrowers are more likely to pay off debt and refinance at the lower interest rates then available. Unscheduled prepayments shorten the average lives of mortgage-related and other asset-backed securities and may result in the Portfolio’s having to reinvest the proceeds of the prepayments at lower interest rates, thereby reducing the Portfolio’s income.
Target 2035 Allocation Portfolio | Non-Investment Grade Securities Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Non-Investment Grade Securities Risk —  Bonds rated below BBB by Standard & Poor’s Global Ratings or Fitch Ratings, Ltd., or below Baa by Moody’s Investors Service, Inc. (or, if unrated, determined by the investment manager to be of comparable quality) are speculative in nature and are subject to additional risk factors such as increased possibility of default, illiquidity of the security, and changes in value based on changes in interest rates. Non-investment grade bonds, sometimes referred to as “junk bonds,” are usually issued by companies without long track records of sales and earnings, or by those companies with questionable credit strength. The creditworthiness of issuers of non-investment grade debt securities may be more complex to analyze than that of issuers of investment grade debt securities, and reliance on credit ratings may present additional risks.
Target 2035 Allocation Portfolio | Portfolio Management Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Portfolio Management Risk —  The Portfolio is subject to the risk that strategies used by an investment manager and its securities selections fail to produce the intended results. An investment manager’s judgments or decisions about the quality, relative yield or value of, or market trends affecting, a particular security or issuer, industry, sector, region or market segment, or about the economy or interest rates, may be incorrect or otherwise may not produce the intended results, which may result in losses to the Portfolio. In addition, many processes used in Portfolio management, including security selection, rely, in whole or in part, on the use of various technologies. The Portfolio may suffer losses if there are imperfections, errors or limitations in the quantitative, analytic or other tools, resources, information and data used, or the analyses employed or relied on, by an investment manager, or if such tools, resources, information or data are used incorrectly, fail to produce the desired results, or otherwise do not work as intended. There can be no assurance that the use of these technologies will result in effective investment decisions for the Portfolio. In addition, the Portfolio could experience losses if an investment manager’s judgments about the risks associated with the Portfolio’s investment program prove to be incorrect.
Target 2035 Allocation Portfolio | Prepayment Risk and Extension Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Prepayment Risk and Extension Risk —  Prepayment risk is the risk that the issuer of a security held by the Portfolio may pay off principal more quickly than originally anticipated. This may occur when interest rates fall. The Portfolio may have to reinvest the proceeds in an investment offering a lower yield, may not benefit from any increase in value that might otherwise result from declining interest rates and may lose any premium it paid to acquire the security. Extension risk is the risk that the issuer of a security held by the Portfolio may pay off principal more slowly than originally anticipated. This may occur when interest rates rise. The Portfolio may be prevented from reinvesting the proceeds it would have received at a given time in an investment offering a higher yield.
Target 2035 Allocation Portfolio | Redemption Risk [Member]  
Risk Return Abstract rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Redemption Risk —  The Portfolio may experience periods of heavy redemptions that could cause the Portfolio to sell assets at inopportune times or at a loss or depressed value. Redemption risk is heightened during periods of declining or illiquid markets. Heavy redemptions could hurt the Portfolio’s performance. Market developments and other factors, including a general rise in interest rates, have the potential to cause investors to move out of fixed income securities on a large scale, which may increase redemptions from mutual funds that hold large amounts of fixed income securities. The market-making capacity of dealers has been reduced in recent years, in part as a result of structural changes, such as fewer proprietary trading desks at broker-dealers and increased regulatory capital requirements. Increased redemptions from mutual funds that hold large amounts of fixed income securities, coupled with a reduction in the ability or willingness of dealers and other institutional investors to buy or hold fixed income securities, may result in decreased liquidity and increased volatility in the fixed income markets.
Target 2035 Allocation Portfolio | Class IB  
Risk Return Abstract rr_RiskReturnAbstract  
Shareholder Fees (fees paid directly from your investment) rr_ShareholderFeeOther
Management Fee rr_ManagementFeesOverAssets 0.10%
Distribution and/or Service Fees (12b-1 fees) rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.19%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.50%
Total Annual Portfolio Operating Expenses rr_ExpensesOverAssets 1.04%
1 Year rr_ExpenseExampleYear01 $ 106
3 Years rr_ExpenseExampleYear03 331
5 Years rr_ExpenseExampleYear05 574
10 Years rr_ExpenseExampleYear10 $ 1,271
2015 rr_AnnualReturn2015 (1.98%)
2016 rr_AnnualReturn2016 7.94%
2017 rr_AnnualReturn2017 17.78%
2018 rr_AnnualReturn2018 (7.14%)
2019 rr_AnnualReturn2019 22.28%
2020 rr_AnnualReturn2020 13.70%
2021 rr_AnnualReturn2021 14.10%
2022 rr_AnnualReturn2022 (16.32%)
2023 rr_AnnualReturn2023 16.56%
2024 rr_AnnualReturn2024 11.49%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel <span style="color:#000000;font-family:Arial;font-size:8pt;margin-left:0.0pt;">Best quarter (% and time period)</span>
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 16.05%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel <span style="color:#000000;font-family:Arial;font-size:8pt;margin-left:0.0pt;">Worst quarter (% and time period)</span>
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (17.89%)
OneYear rr_AverageAnnualReturnYear01 11.49%
FiveYears rr_AverageAnnualReturnYear05 7.13%
TenYears rr_AverageAnnualReturnYear10 7.16%
Target 2035 Allocation Portfolio | Class K  
Risk Return Abstract rr_RiskReturnAbstract  
Shareholder Fees (fees paid directly from your investment) rr_ShareholderFeeOther
Management Fee rr_ManagementFeesOverAssets 0.10%
Distribution and/or Service Fees (12b-1 fees) rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.19%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.50%
Total Annual Portfolio Operating Expenses rr_ExpensesOverAssets 0.79%
1 Year rr_ExpenseExampleYear01 $ 81
3 Years rr_ExpenseExampleYear03 252
5 Years rr_ExpenseExampleYear05 439
10 Years rr_ExpenseExampleYear10 $ 978
OneYear rr_AverageAnnualReturnYear01 11.76%
FiveYears rr_AverageAnnualReturnYear05 7.38%
TenYears rr_AverageAnnualReturnYear10 7.42%
Target 2035 Allocation Portfolio | S&P 500® Index (reflects no deduction for fees, expenses, or taxes)  
Risk Return Abstract rr_RiskReturnAbstract  
OneYear rr_AverageAnnualReturnYear01 25.02%
FiveYears rr_AverageAnnualReturnYear05 14.53%
TenYears rr_AverageAnnualReturnYear10 13.10%
Target 2035 Allocation Portfolio | S&P Target Date 2035 Index (reflects no deduction for fees, expenses, or taxes)  
Risk Return Abstract rr_RiskReturnAbstract  
OneYear rr_AverageAnnualReturnYear01 11.39%
FiveYears rr_AverageAnnualReturnYear05 7.44%
TenYears rr_AverageAnnualReturnYear10 7.60%