The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Portfolio’s performance. During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 224% of the average value of the portfolio.

Expenses Restated to Reflect Current [Text]

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Expenses have been restated to reflect current fees.

Expense Example Narrative [Text Block]

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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, that the Portfolio’s operating expenses remain the same, and that the Expense Limitation Arrangement is not renewed. 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 Narrative [Text Block]

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Under normal circumstances, the Portfolio invests at least 80% of its net assets in inflation-indexed bonds of varying maturities issued by the U.S. and non-U.S. governments, their agencies or instrumentalities and corporations, which may be represented by forwards or derivatives such as options, futures contracts or swap agreements. Inflation-indexed bonds are fixed income securities that are structured to provide protection against inflation. The value of the bonds’ principal or the interest income paid on the bonds is adjusted to track changes in an official inflation measure. Assets not invested in inflation-indexed bonds may be invested in other types of fixed income instruments, including bonds, debt securities, including variable and floating rate securities, and other similar instruments issued by various U.S. and non-U.S. public- or private-sector entities.

The Portfolio invests primarily in investment-grade debt securities, but may invest up to 10% of its total assets in high yield securities, also known as “junk bonds,” rated B or higher by Moody’s Investors Service, Inc. (“Moody’s”), or equivalently rated by Standard & Poor’s Global Rating (“S&P”) or Fitch, Inc. (“Fitch”), or, if unrated, determined by the Adviser or the Sub-Adviser to be of comparable quality (except that within such 10% limitation, the Portfolio may invest in mortgage-related securities rated below B).

The Portfolio also may invest up to 30% of its total assets in securities denominated in foreign currencies and may invest beyond this limit in U.S. dollar denominated securities of foreign issuers. The Portfolio may invest up to 10% of its total assets in securities and instruments that are economically tied to emerging market countries (this limitation does not apply to investment grade sovereign debt denominated in the local currency with less than one year remaining to maturity, which means the Portfolio may invest, together with any other investments denominated in foreign currencies, up to 30% of its total assets in such instruments). The Portfolio will normally limit its foreign currency exposure (from non-U.S. dollar denominated securities or currencies) to 20% of its total assets.

Subject to applicable law and any other restrictions described in the Portfolio’s Prospectus or Statement of Additional Information, the Portfolio may invest, without limitation, in derivative instruments, such as options, futures contracts or swap agreements, or in mortgage- or asset-backed securities. The Portfolio’s investments in derivatives may be deemed to involve the use of leverage because the Portfolio is not required to invest the full market value of the contract upon entering into the contract but participates in gains and losses on the full contract price. The use of derivatives also may be deemed to involve the use of leverage because the heightened price sensitivity of some derivatives to market changes may magnify the Portfolio’s gain or loss. It is not expected, however, that the Portfolio will be leveraged by borrowing money for investment purposes. The Portfolio’s investments in derivatives may require it to maintain a percentage of its assets in cash, cash equivalent instruments or other liquid assets to serve as margin or collateral for the Portfolio’s obligations under derivative transactions.

The Portfolio may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as “sale-buyback” or “dollar roll” transactions). In sale-buyback and dollar roll transactions, the Portfolio sells a security to another party and simultaneously agrees to repurchase the same security (in the case of a sale-buyback) or a similar, but not the same, security (in the case of a dollar roll) on a specified date and pre-determined price. The Portfolio may purchase or sell securities on a when-issued, delayed delivery or forward commitment basis and may engage in short sales. The Portfolio may also invest up to 10% of its total assets in preferred securities.

The U.S. Treasury uses the Consumer Price Index for Urban Consumers as the inflation measure. Inflation-indexed bonds issued by a foreign government are generally adjusted to reflect a comparable inflation index, calculated by that government. “Real return” equals total return less the estimated cost of inflation, which is typically measured by the change in an official inflation measure. Duration is a measure used to determine the sensitivity of a security’s price to changes in interest rates. 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. Effective duration, a common method of calculating duration, takes into account that for certain bonds expected cash flows will fluctuate as interest rates change and is defined in nominal yield terms, which is market convention for most bond investors and managers. Because market convention for bonds is to use nominal yields to measure effective duration, effective duration for real return bonds, which are based on real yields, are converted through a conversion factor. The resulting nominal duration typically can range from 20% and 90% of the respective real duration. All security holdings will be measured in nominal effective duration terms. Similarly, the effective duration of the Bloomberg Barclays U.S. TIPS Index will be calculated using the same conversion factors. The effective duration of the Portfolio normally varies within three years (plus or minus) of the effective duration of the securities comprising the Bloomberg Barclays U.S. TIPS Index, as calculated by the Sub-Adviser, which as of December 31, 2019, as converted, was 7.36 years.

The Portfolio also may lend its portfolio securities to earn additional income.

Risk Narrative [Text Block]

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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. The value of your investment may fall, sometimes sharply, and you could lose money by investing in the Portfolio. There can be no assurance that the Portfolio will achieve its investment objective.

The following risks can negatively affect the Portfolio’s performance. The most significant risks are listed first, followed by additional risks in alphabetical order.

Interest Rate Risk: Changes in interest rates may affect the yield, liquidity and value of investments in income producing or debt 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 or duration 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 with any increase in the duration of those securities. A significant or rapid rise in interest rates could result in losses to the Portfolio.

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, 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.

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. Derivatives can be difficult to value, and valuation may be more difficult in times of market turmoil. Changing regulation may make derivatives more costly, limit their availability, impact the Portfolio’s ability to maintain its investments in derivatives, disrupt markets, or otherwise adversely affect their value or performance.

Inflation-Indexed Bonds Risk: Inflation-indexed bonds are fixed income securities whose principal value is periodically adjusted according to inflation. Inflation-indexed bonds, including Treasury inflation-indexed securities, decline in value when real interest rates rise. In certain interest rate environments, such as when real interest rates are rising faster than nominal interest rates, inflation-indexed bonds may experience greater losses than other fixed income securities with similar durations. Interest payments on inflation-linked debt securities can be unpredictable and may vary as the principal and/or interest is adjusted for inflation. In periods of deflation, the Portfolio may have no income at all from such investments.

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. In addition, certain mortgage-related and other asset-backed securities may include securities backed by pools of loans made to “subprime” borrowers or borrowers with blemished credit histories. The risk of defaults by borrowers is generally higher in the case of asset or mortgage pools that include subprime assets or mortgages, and the liquidity and value of subprime mortgages and non-investment grade mortgage-backed securities that are not guaranteed by Ginnie Mae, Fannie Mae, and Freddie Mac could change dramatically over time. 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.

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. government. 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 the Portfolio holds does not apply to the market value of the security or to shares of the Portfolio. A security backed by the U.S. Treasury or the full faith and credit of the U.S. government is guaranteed only as to the timely payment of interest and principal when held to maturity.

Short Position Risk: The Portfolio may engage in short sales and may enter into derivative contracts that have a similar economic effect (e.g., taking a short position in a futures contract). The Portfolio will incur a loss as a result of a short position if the price of the asset sold short increases between the date of the short position sale and the date on which an offsetting position is purchased. Short positions may be considered speculative transactions and involve special risks that could cause or increase losses or reduce gains, including greater reliance on the investment adviser’s ability to accurately anticipate the future value of a security or instrument, potentially higher transaction costs, and imperfect correlation between the actual and desired level of exposure. Because the Portfolio’s potential loss on a short position arises from increases in the value of the asset sold short, the extent of such loss, like the price of the asset sold short, is theoretically unlimited. By investing the proceeds received from selling securities short, a Portfolio could be deemed to be employing a form of leverage, in that it amplifies changes in the Portfolio’s net asset value because it increases the Portfolio’s exposure to the market and may increase losses and the volatility of returns.

Cash Management Risk: Upon entering into certain derivatives contracts, such as futures contracts, and to maintain open positions in certain derivatives contracts, the Portfolio may be required to post collateral for the contract, the amount of which may vary. In addition, the Portfolio may maintain cash and cash equivalent positions as part of the Portfolio’s strategy in order to take advantage of investment opportunities as they arise, to manage the Portfolio’s market exposure and for other portfolio management purposes. As such, the Portfolio may maintain cash balances, which may be significant, with counterparties such as the Trust’s custodian or its affiliates. Maintaining larger cash and cash equivalent positions could negatively affect the Portfolio’s performance due to missed investment opportunities and may also subject the Portfolio to additional risks, such as increased credit risk with respect to the custodian bank holding the assets and the risk that a counterparty may be unable or unwilling to honor its obligations.

Dollar Roll and Sale-Buyback Transactions. Dollar roll and sale-buyback transactions may increase the Portfolio’s volatility and may be viewed as a form of leverage. There is also a risk that the counterparty will be unable or unwilling to complete the transaction as scheduled, which may result in losses to the Portfolio.

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.

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 trade barriers and other protectionist trade policies (including those of the U.S.), governmental instability, or other political or economic actions, also may adversely impact security values. World markets, or those in a particular region, may all react in similar fashion to important economic or political 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.

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.

Emerging Markets Risk: Investments in emerging market countries are more susceptible to loss than investments in more developed foreign countries and may present market, credit, currency, liquidity, legal, political, technical and other risks different from, or greater than, the risks of investing in more developed foreign countries. Emerging market countries may be more likely to experience rapid and significant adverse developments in their political or economic structures, restrict foreign investments, impose high withholding or other taxes on foreign investments, impose restrictive exchange control regulations, or nationalize or expropriate the assets of private companies, which may have negative impacts on transaction costs, market price, investment returns and the legal rights and remedies of the Portfolio. In addition, the securities markets of emerging market countries generally are smaller, less liquid and more volatile than those of more developed foreign countries, and emerging market countries often have less uniformity in accounting, auditing and financial reporting requirements and less reliable clearance and settlement, registration and custodial procedures. Securities of issuers traded on foreign exchanges may be suspended. The likelihood of such suspensions may be higher for securities of issuers in emerging market countries than in countries with more developed markets.

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, 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. The United Kingdom (“UK”) left the EU on January 31, 2020, commonly referred to as “Brexit.” The effect on the UK’s economy will likely depend on the nature of trade relations with the EU following its exit, a matter that is being negotiated. There is significant market uncertainty regarding Brexit’s ramifications, and the range and potential implications of possible political, regulatory, economic, and market outcomes cannot be fully known. The negative impact on not only the UK and European economies but also the broader global economy could be significant, potentially resulting in increased volatility and illiquidity, which could adversely affect the value of the Portfolio’s investments. Any further withdrawals from the EU could cause additional market disruption globally.

Geographic Concentration Risk: To the extent the Portfolio invests a significant portion of its assets in securities of companies domiciled, or exercising the predominant part of their economic activity, in one country or geographic region, it assumes the risk that economic, political, social and environmental conditions in that particular country or region will have a significant impact on the Portfolio’s investment performance and that the Portfolio’s performance will be more volatile than the performance of more geographically diversified funds. In addition, the risks associated with investing in a narrowly defined geographic area are generally more pronounced with respect to investments in emerging market countries.

Investment Grade Securities Risk: Securities rated in the lower investment grade rating categories (e.g., BBB or Baa) are considered investment grade securities, but are somewhat riskier 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.

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.

LIBOR Risk: The publication of the London Interbank Offered Rate (LIBOR), which many debt securities, derivatives and other financial instruments use as the reference or benchmark rate for interest rate calculations, is expected to be discontinued at the end of 2021. The transition process away from LIBOR may lead to increased volatility and illiquidity in markets that currently rely on LIBOR to determine interest rates, and the eventual use of an alternative reference rate may adversely affect the Portfolio’s performance. In addition, the usefulness of LIBOR may deteriorate in the period leading up to its discontinuation, which could adversely affect the liquidity or market value of securities that use LIBOR.

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 a loss 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.

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. Changes in the financial condition of a single issuer can impact a market as a whole. Geo-political risks, including terrorism, tensions or open conflict between nations, or political or economic dysfunction within some nations that are major players on the world stage, may lead to instability in world economies and markets, may lead to increased market volatility, and may have adverse long-term effects. Events such as natural disasters or pandemics, and governments’ reactions to such events, could cause uncertainty in the markets and may adversely affect the performance of the global economy. 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.

New Portfolio Risk: The Portfolio is newly or recently established and has limited operating history. The Portfolio may not be successful in implementing its investment strategy, and there can be no assurance that the Portfolio will grow to or maintain an economically viable size, which could result in the Portfolio being liquidated at any time without shareholder approval and at a time that may not be favorable for all shareholders.

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.

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.

Portfolio Turnover Risk: High portfolio turnover (generally, turnover in excess of 100% in any given fiscal year) may result in increased transaction costs to the Portfolio, which may result in higher fund expenses and lower total return.

Preferred Stock Risk: Preferred stock is subject to many of the risks associated with debt securities, including interest rate risk. Unlike interest payments on debt securities, dividends on preferred stock are generally payable at the discretion of the issuer’s board of directors. Preferred shareholders may have certain rights if dividends are not paid but generally have no legal recourse against the issuer. Shareholders may suffer a loss of value if dividends are not paid. In certain situations an issuer may call or redeem its preferred stock or convert it to common stock. The market prices of preferred stocks are generally more sensitive to actual or perceived changes in the issuer’s financial condition or prospects than are the prices of debt securities.

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.

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. In addition, significant securities market disruptions related to outbreaks of the coronavirus disease (COVID-19) have led to dislocation in the market for a variety of fixed income securities (including, without limitation, commercial paper, corporate debt securities, certificates of deposit, asset-backed debt securities and municipal obligations), which has decreased liquidity and sharply reduced returns. 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.

Securities Lending Risk: The Portfolio may lend its portfolio securities to seek income. There is a risk that a borrower may default on its obligations to return loaned securities. The Portfolio will be responsible for the risks associated with the investment of cash collateral and may lose money on its investment of cash collateral or may fail to earn sufficient income on its investment to meet obligations to the borrower. Securities lending may introduce leverage into the Portfolio. In addition, delays may occur in the recovery of loaned securities from borrowers, which could interfere with the Portfolio’s ability to vote proxies or to settle transactions.

Sovereign Debt Securities Risk: Sovereign debt securities are subject to the risk that a governmental entity may delay or refuse to pay interest or principal on its sovereign debt. There is no legal process for collecting sovereign debt that a government does not pay nor are there bankruptcy proceedings through which all or part of the sovereign debt that a governmental entity has not repaid may be collected. Sovereign debt risk is increased for emerging market issuers.

Variable and Floating Rate Securities Risk: The market prices of securities with variable and floating interest rates are generally less sensitive to interest rate changes than are the market prices of securities with fixed interest rates. Variable and floating rate securities may decline in value if market interest rates or interest rates paid by such securities do not move as expected. Conversely, variable and floating rate securities will not generally rise in value if market interest rates decline. Certain types of floating rate securities may be subject to greater liquidity risk than other debt securities.

When-Issued and Delayed Delivery Securities and Forward Commitments Risk: When-issued and delayed delivery securities and forward commitments involve the risk that the security the Portfolio buys will decline in value prior to its delivery. This risk is in addition to the risk that the Portfolio’s other assets will decline in value. Therefore, these transactions may result in a form of leverage and increase the Portfolio’s overall investment exposure. There also is the risk that the security will not be issued or that the other party to the transaction will not meet its obligation. If this occurs, the Portfolio may lose both the investment opportunity for the assets it set aside to pay for the security and any gain in the security’s price.

Risk Not Insured Depository Institution [Text]

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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.

Performance Narrative [Text Block]

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The bar chart below shows the Portfolio’s first calendar year of performance. The table below provides some indication of the risks of investing in the Portfolio by showing how the Portfolio’s average annual total returns for the past one-year and since inception periods through December 31, 2019 compared to the returns of a broad-based securities market index. Past performance is not an indication of future performance.

Class K shares have not commenced operations as of the date of this Prospectus.

The performance results do not reflect any Contract-related fees and expenses, which would reduce the performance results.

Performance Past Does Not Indicate Future [Text]

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Past performance is not an indication of future performance.

Bar Chart Closing [Text Block]

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