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 and then redeem all of your shares at the end of these periods. The Example also assumes that your investment has a 5% return each year, 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 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, plus any borrowings for investment purposes, in fixed income securities. For purposes of this investment policy, fixed income securities include direct and indirect investments in fixed income securities and investments in other investment companies and financial instruments that drive their value from such securities. The Portfolio’s investments in fixed income securities include, but are not limited to, securities issued or guaranteed by the U.S. government or its agencies, instrumentalities or sponsored corporations; mortgage-backed securities; asset-backed securities; foreign and domestic corporate bonds; floating or variable rate obligations (including inverse floater collateralized mortgage obligations); bank loans; fixed income securities issued by corporations and governments in foreign countries including emerging markets issuers and U.S. dollar-denominated securities or non-U.S. issuers; securities issued by municipalities; collateralized loan obligations and other securities bearing fixed interest rates of any maturity.

The Portfolio may invest up to 40% of its assets in below investment grade securities (commonly known as “junk bonds”). Such investments may include debt obligations of distressed companies, including companies that are close to or in default. The Sub-Adviser allocates investments in below investment grade securities broadly by industry and issuer in an attempt to reduce the impact on the Portfolio of negative events affecting an industry or issuer. Securities below investment grade include those securities rated Ba1 or lower by Moody’s Investors Service, Inc. (“Moody’s”) or BB+ or lower by Fitch Ratings Ltd. (“Fitch”) or by Standard & Poor’s Ratings Services (“S&P”) or, if unrated, deemed to be of comparable quality by the Sub-Adviser. The Portfolio may invest in mortgage-backed or other asset-backed securities of any credit rating or credit quality without regard to the 40% limitation described above.

The Portfolio may also invest in inverse floaters, interest-only and principal-only securities. In addition, the Portfolio may invest in senior bank loans and assignments, including through investments in other investment companies advised by the Sub-Adviser.

The Sub-Adviser actively manages the Portfolio’s asset class exposure using a top-down approach, which involves using fundamental research regarding the investment characteristics of each sector (such as risk, volatility, relative valve, and the potential for growth and income), as well as the Sub-Adviser’s outlook for the economy and financial markets as a whole. Primary sectors include government/municipals, high yield, global developed credit, international sovereign debt, emerging markets, and mortgage- and asset-backed. The Sub-Adviser will gradually rotate portfolio assets among sectors in various markets using a long-term approach to attempt to maximize return. Individual securities within asset classes are selected using a bottom up approach, which involves an analysis of each individual issuer’s creditworthiness.

The Sub-Adviser uses a controlled risk approach in managing the Portfolio, which includes consideration of:

Security selection within a given asset class

Relative performance of the various market sectors and asset classes

The rates offered by bonds at different maturities

Fluctuations in the overall level of interest rates

The Sub-Adviser also monitors the duration of the securities held by the Portfolio to seek to mitigate exposure to interest rate risk. Duration is a measure used to determine the sensitivity of a security’s price to interest rates. Typically, a bond portfolio with a low (short) duration means that its value is less sensitive to interest rate changes, while a bond portfolio with a high (long) duration is more sensitive. Under normal circumstances, the Sub-Adviser seeks to maintain an investment portfolio with a weighted average effective duration of no less than two years and no more than eight years. The duration of the Portfolio’s investments may vary materially from its target, from time to time, and there is no assurance that the duration of the Portfolio’s investments will meet its target.

Portfolio securities may be sold at any time. Sales may occur when the Sub-Adviser perceives deterioration in the credit fundamentals of the issuer, believes there are negative macro political considerations that may affect the issuer, determines to take advantage of a better investment opportunity, or the individual security has reached the Sub-Adviser’s sell target. The Portfolio may engage in active and frequent trading of portfolio securities to achieve its investment objective.

The Manager has been granted relief by the Securities and Exchange Commission to hire, terminate and replace Sub-Advisers and amend advisory agreements subject to the approval of the Board of Trustees and without obtaining shareholder approval. However, the Manager may not enter into an advisory agreement on behalf of the Portfolio with an “affiliated person” of the Manager, such as AllianceBernstein L.P., unless the advisory agreement is approved by the Portfolio’s shareholders. The Manager is responsible for overseeing Sub-Advisers and recommending their hiring, termination and replacement to the Board of Trustees.

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. You may lose money by investing in the Portfolio. Performance may be affected by one or more of the following risks.

Bank Loans Risk: Loans are subject to additional risks including liquidity risk, prepayment risk (the risk that when interest rates fall, debt securities may be repaid more quickly than expected and a Portfolio may be required to reinvest in securities with a lower yield), extension risk (the risk that when interest rates rise, debt securities may be repaid more slowly than expected and the value of a Portfolio's holdings may decrease), the risk of subordination to other creditors, restrictions on resale, and the lack of a regular trading market and publicly available information. In addition, liquidity risk may be more pronounced for a Portfolio investing in loans because certain loans may have a more limited secondary market. These loans may be difficult to value.

Collateralized Loan Obligations Risk: In addition to the typical risks associated with fixed income securities discussed elsewhere in this Prospectus (e.g., interest rate risk and credit risk), collateralized loan obligations ("CLOs") carry additional risks including, but are not limited to: (i) the possibility that distributions from collateral securities will not be adequate to make interest or other payments; (ii) the quality of the collateral may decline in value or default; (iii) the risk that the Portfolio may invest in CLOs that are subordinate to other classes; and (iv) the complex structure of the security may not be fully understood at the time of investment and may produce disputes with the issuer or unexpected investment results.

Credit Risk: The risk that the issuer or the guarantor (or other obligor, such as a party providing insurance or other credit enhancement) of a fixed income security, or the counterparty to a derivatives contract, repurchase agreement, loan of portfolio securities or other transaction, is unable or unwilling, or is perceived (whether by market participants, ratings agencies, pricing services or otherwise) as unable or unwilling, to make timely principal and/or interest payments, or otherwise honor its obligations. Securities are subject to varying degrees of credit risk, which are often reflected in their credit ratings. The downgrade of the credit rating of a security may decrease its value.

Distressed Companies Risk: Debt obligations of distressed companies typically are unrated, lower-rated, in default or close to default. Also, securities of distressed companies may be less liquid and are generally more likely to become worthless than the securities of more financially stable companies. If the issuer of a security held by a Portfolio defaults, the Portfolio may experience significant losses on the security, which may lower the Portfolio's NAV. Securities tend to lose much of their value before the issuer defaults.

Foreign Securities Risk: Investments in foreign securities, including depositary receipts, involve risks not associated with investing in U.S. securities. Foreign markets, particularly emerging markets, may be less liquid, more volatile and subject to less government supervision than domestic markets. 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 also may impact security values and it may take more time to clear and settle trades involving foreign securities.

Emerging Markets Risk: There are greater risks involved in investing in emerging market countries and/or their securities markets. Investments in these countries and/or markets may present market, credit, currency, liquidity, legal, political, technical and other risks different from, or greater than, the risks of investing in developed countries. 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.

Geographic Concentration Risk: A Portfolio that 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 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. The economies and financial markets of certain regions can be highly interdependent and may decline all at the same time. In addition, certain areas are prone to natural disasters such as earthquakes, volcanoes, droughts or tsunamis and are economically sensitive to environmental events.

Political/Economic Risk: Changes in economic and tax policies, government instability, war or other political or economic actions or factors may have an adverse effect on a Portfolio's foreign investments.

Regulatory Risk: Less information may be available about foreign companies. In general, foreign companies are not subject to uniform accounting, auditing and financial reporting standards or to other regulatory practices and requirements as are U.S. companies. Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws. In addition, some countries may have legal systems that may make it difficult for the Portfolio to vote proxies, exercise shareholder rights, and pursue legal remedies with respect to its foreign investments.

Settlement Risk: Settlement and clearance procedures in certain foreign markets differ significantly from those in the United States. Foreign settlement and clearance procedures and trade regulations also may involve certain risks (such as delays in payment for or delivery of securities) not typically associated with the settlement of U.S. investments. At times, settlements in certain foreign countries have not kept pace with the number of securities transactions. These problems may make it difficult for a portfolio to carry out transactions. If a portfolio cannot settle or is delayed in settling a purchase of securities, it may miss attractive investment opportunities and certain of its assets may be uninvested with no return earned thereon for some period. If a Portfolio cannot settle or is delayed in settling a sale of securities, it may lose money if the value of the security then declines or, if it has contracted to sell the security to another party, the Portfolio could be liable for any losses incurred.

Transaction Costs Risk: The costs of buying and selling foreign securities, including tax, brokerage and custody costs, generally are higher than those involving domestic transactions.

Interest Rate Risk: The risk that fixed income securities will decline in value because of changes in interest rates. When interest rates decline, the value of a Portfolio's debt securities generally rises. Conversely, when interest rates rise, the value of the Portfolio's debt securities generally declines. A Portfolio with a longer average duration will be more sensitive to changes in interest rates, usually making it more volatile than a fund with a shorter average duration. As of the date of this Prospectus, interest rates in the United States are at or near historic lows, but may rise significantly or rapidly, potentially resulting in losses to the Portfolio.

Inverse Floaters Risk: Inverse floaters, which are fixed income securities with a floating or variable rate of interest, may exhibit substantially greater price volatility than fixed rate obligations having similar credit quality, redemption provisions and maturity, and inverse floater collateralized mortgage obligations ("CMOs") exhibit greater price volatility than the majority of mortgage-related securities. The interest rate of an inverse floater is tied to an interest rate index and tends to move in the opposite direction as changes in the reference index. In addition, some inverse floater CMOs exhibit extreme sensitivity to changes in prepayments. As a result, the yield to maturity of an inverse floater CMO is sensitive not only to changes in interest rates but also to changes in prepayment rates on the related underlying mortgage assets.

Investment Grade Securities Risk: Debt securities commonly are rated by national bond ratings agencies. Investment grade securities are securities rated BBB or higher by S&P or Fitch or Baa or higher by Moody's. 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, and are considered to lack outstanding investment characteristics.

Non-Investment Grade Securities Risk: Bonds rated below investment grade (i.e., BB or lower by S&P or Fitch or Ba or lower by Moody's or, if unrated, are deemed to be of comparable quality by a Sub-Adviser) 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.

Liquidity Risk: The risk that certain investments may be difficult or impossible for a Portfolio to purchase or sell at an advantageous time or price or in sufficient amounts to achieve the desired level of exposure, or possibly requiring the Portfolio to dispose of other investments at unfavorable times or prices to satisfy obligations which may result in a loss or may be costly to the Portfolio.

Mortgage-Backed and Asset-Backed Securities Risk: The risk that the principal on mortgage- and asset-backed securities held by a Portfolio will be prepaid, which generally will reduce the yield and market value of these securities. If interest rates fall, the rate of prepayments tends to increase as borrowers are motivated to pay off debt and refinance at new lower rates. Rising interest rates may increase the risk of default by borrowers and tend to extend the duration of these securities, making them more sensitive to changes in interest rates. As a result, in a period of rising interest rates, a Portfolio that holds these types of securities may experience additional volatility and losses. This is known as extension risk. Moreover, declines in the credit quality of the issuers of mortgage- and asset-backed securities or instability in the markets for such securities may affect the value and liquidity of such securities, which could result in losses to 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 a Portfolio, which may result in higher fund expenses and lower total return.

Redemption Risk: A 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 a 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. Such a move, 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.

Risks of Investing in Other Investment Companies: A Portfolio that invests in other investment companies will indirectly bear fees and expenses charged by those investment companies, in addition to the Portfolio's direct fees and expenses. The cost of investing in the Portfolio, therefore, may be higher than the cost of investing in a mutual fund that exclusively invests directly in individual stocks and bonds. In addition, the Portfolio's net asset value is subject to fluctuations in the net asset values of the other investment companies in which it invests. The Portfolio is also subject to the risks associated with the securities in which the other investment companies invest and the ability of the Portfolio to meet its investment objective will depend, to a significant degree, on the ability of the other investment companies to meet their investment objectives. The Portfolio and the other investment companies are subject to certain general investment risks, including market risk, issuer-specific risk, investment style risk and portfolio management risk. In addition, to the extent a Portfolio invests in other investment companies 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 such as equity risk, market capitalization risk, investment grade securities risk, interest rate risk, credit/default risk, foreign investing and emerging markets securities risk and non-investment grade securities risk. The extent to which the investment performance and risks associated with the Portfolio correlate to those of a particular other investment company will depend upon the extent to which the Portfolio's assets are allocated from time to time for investment in the other investment company, which will vary.

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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Performance information will be available in the Prospectus after the Portfolio has been in operation for one full calendar year.