This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. Because the information does not reflect deductions at the separate account level or contract level for any charges that may be incurred under a contract, Contractholders that invest in the Portfolio should refer to the variable contract prospectus for a description of fees and expenses that apply to Contractholders. Inclusion of these charges would increase the fees and expenses provided below.

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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Annual Portfolio Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

May 1, 2022

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, 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]

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Examples

Expense Example Narrative [Text Block]

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The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio’s operating expenses stay the same and that any fee waiver and/or expense limitation is in effect for only the first year. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy [Heading]

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PRINCIPAL STRATEGIES

Strategy Narrative [Text Block]

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The Portfolio invests in a globally diversified portfolio of equity and debt securities, including exchange-traded funds, or ETFs, and other financial instruments, and expects to enter into derivatives transactions, such as options, futures contracts, forwards, and swaps to achieve market exposure. The Portfolio’s neutral weighting, from which it will make its tactical asset allocations, is 60% equity exposure and 40% debt exposure. Within these broad components, the Portfolio may invest in any type of security, including common and preferred stocks, warrants and convertible securities, government and corporate fixed-income securities, commodities, currencies, real estate-related securities and inflation-indexed securities. The Portfolio may invest in U.S., non-U.S. and emerging market issuers. The Portfolio may invest in securities of companies across the capitalization spectrum, including smaller capitalization companies. The Portfolio expects its investments in fixed-income securities to have a broad range of maturities and quality levels. The Portfolio is expected to be highly diversified across industries, sectors and countries, and will choose its positions from several market indices worldwide in a manner that is intended to track the performance (before fees and expenses) of those indices.

The Adviser will continuously monitor the risks presented by the Portfolio’s asset allocation and may make frequent adjustments to the Portfolio’s exposures to different asset classes. Using its proprietary Dynamic Asset Allocation techniques, the Adviser employs a discretionary volatility reduction/management strategy intended to reduce overall volatility and limit downside exposure. The Adviser adjusts the Portfolio’s exposure to the equity and debt markets, and to segments within those markets, in response to the Adviser’s assessment of the relative risks and returns of those segments. For example, when the Adviser determines that equity market volatility is particularly low and that, therefore, the equity markets present reasonable return opportunities, the Adviser may increase the Portfolio’s equity exposure to as much as 80%. Conversely, when the Adviser determines that the risks in the equity markets are disproportionately greater than the potential returns offered, the Adviser may reduce the Portfolio’s equity exposure significantly below the target percentage or may even decide to eliminate equity exposure altogether by increasing the Portfolio’s fixed-income exposure to 100%. This investment strategy is intended to reduce the Portfolio’s overall investment risk, but may at times result in the Portfolio underperforming the markets.

The Portfolio expects to utilize derivatives and to invest in ETFs to a significant extent. Derivatives and ETFs may provide more efficient and economical exposure to market segments than direct investments, and the Portfolio’s market exposures may at times be achieved almost entirely through the use of derivatives or through the investments in ETFs. Derivatives transactions and ETFs may also be a quicker and more efficient way to alter the Portfolio’s exposure than buying and selling direct investments. As a result, the Adviser expects to use derivatives as one of the primary tools for adjusting the Portfolio’s exposure levels from its neutral weighting. The Adviser also expects to use direct investments and ETFs to adjust the Portfolio’s exposure levels. In determining when and to what extent to enter into derivatives transactions or to invest in ETFs, the Adviser considers factors such as the relative risks and returns expected of potential investments and the cost of such transactions. The Adviser considers the impact of derivatives and ETFs in making its assessment of the Portfolio’s risks.

Currency exchange rate fluctuations can have a dramatic impact on returns, significantly adding to returns in some years and greatly diminishing them in others. To the extent that the Portfolio invests in non-U.S. Dollar-denominated investments, the Adviser will integrate the risks of foreign currency exposures into its investment and asset allocation decision making. The Adviser may seek to hedge all or a portion of the currency exposure resulting from the Portfolio’s investments. The Adviser may also seek investment opportunities through currencies and currency-related derivatives.

Risk [Heading]

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PRINCIPAL RISKS

Risk Narrative [Text Block]

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•

Market Risk:

The value of the Portfolio’s assets will fluctuate as the stock or bond market fluctuates. The value of its investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events, including public health crises (including the occurrence of a contagious disease or illness), that affect large portions of the market.

•

Interest Rate Risk:

Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. Very low or negative interest rates would likely magnify the risks associated with changes in interest rates. During periods of very low or negative rates, the Portfolio’s returns would likely be adversely affected.

•

Credit Risk:

An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations.

•

Allocation Risk:

The allocation of investments among different global asset classes may have a significant effect on the Portfolio’s net asset value, or NAV, when one of these asset classes is performing more poorly than others. As both the direct investments and derivatives positions will be periodically adjusted to reflect the Adviser’s view of market and economic conditions,

there will be transaction costs that may be, over time, significant. In addition, there is a risk that certain asset allocation decisions may not achieve the desired results and, as a result, the Portfolio may incur significant losses.

•

Foreign (Non-U.S.) Risk:

The Portfolio’s investments in securities of non-U.S. issuers may involve more risk than those of U.S. issuers. These securities may fluctuate more widely in price and may be more difficult to trade due to adverse market, economic, political, regulatory or other factors.

•

Emerging Market Risk:

Investments in emerging market countries may have more risk because the markets are less developed and less liquid, and because these investments may be subject to increased economic, political, regulatory or other uncertainties.

•

Currency Risk:

Fluctuations in currency exchange rates may negatively affect the value of the Portfolio’s investments or reduce its returns.

•

ETF Risk:

ETFs are investment companies. When the Portfolio invests in an ETF, the Portfolio bears its share of the ETF’s expenses and runs the risk that the ETF may not achieve its investment objective.

•

Derivatives Risk:

Derivatives may be difficult to price or unwind and leveraged so that small changes may produce disproportionate losses for the Portfolio. Derivatives, especially

over-the-counter

derivatives, are also subject to counterparty risk.

•

Leverage Risk:

When the Portfolio borrows money or otherwise leverages its portfolio, its NAV may be more volatile because leverage tends to exaggerate the effect of changes in interest rates and any increase or decrease in the value of the Portfolio’s investments. The Portfolio may create leverage through the use of reverse repurchase agreements, forward commitments, or by borrowing money.

•

Illiquid Investments Risk:

Illiquid investments risk exists when certain investments are or become difficult to purchase or sell. Difficulty in selling such investments may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of illiquid investments risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares.

•

Capitalization Risk:

Investments in small- and mid-capitalization companies may be more volatile than investments in large-capitalization companies. Investments in small- and mid-capitalization companies may have additional risks because these companies have limited product lines, markets or financial resources.

•

Real Estate Risk:

The Portfolio’s investments in real estate securities have many of the same risks as direct ownership of real estate, including the risk that the value of real estate could decline due to a variety of factors that affect the real estate market generally. Investments in real estate investment trusts, or REITs, may have additional risks. REITs are dependent on the capability of their managers, may have limited diversification, and could be significantly affected by changes in taxes.

•

Management Risk:

The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions for the Portfolio, but there is no guarantee that its techniques will produce the intended results. Some of these techniques may incorporate, or rely upon, quantitative models, but there is no guarantee that these models will generate accurate forecasts, reduce risk or otherwise perform as expected.

As with all investments, you may lose money by investing in the Portfolio.

Risk Lose Money [Text]

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As with all investments, you may lose money by investing in the Portfolio.

Bar Chart and Performance Table [Heading]

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BAR CHART AND PERFORMANCE INFORMATION

Performance Narrative [Text Block]

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The bar chart and performance information provide an indication of the historical risk of an investment in the Portfolio by showing:

•

how the Portfolio’s performance changed from year to year over the life of the Portfolio; and

•

how the Portfolio’s average annual returns for one year, five years and since inception compare to those of a broad-based securities market index.

The performance information does not take into account separate account charges. If separate account charges were included, an investor’s return would be lower. The Portfolio’s past performance, of course, does not necessarily indicate how it will perform in the future.

Performance Information Illustrates Variability of Returns [Text]

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how the Portfolio’s performance changed from year to year over the life of the Portfolio; and how the Portfolio’s average annual returns for one year, five years and since inception compare to those of a broad-based securities market index.

Performance Additional Market Index [Text]

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The information for the Bloomberg Barclays U.S. Treasury Index and for the composite index is presented to show how the Portfolio’s performance compares with the returns of indices of securities similar to those in which the Portfolio invests.

Performance Past Does Not Indicate Future [Text]

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The Portfolio’s past performance, of course, does not necessarily indicate how it will perform in the future.

Bar Chart [Heading]

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Bar Chart

Bar Chart Does Not Reflect Sales Loads [Text]

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The performance information does not take into account separate account charges. If separate account charges were included, an investor’s return would be lower.

Bar Chart Closing [Text Block]

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Calendar Year End (%) During the period shown in the bar chart, the Portfolio’s: Best Quarter was up 8.23%, 4th quarter, 2020; and Worst Quarter was down -11.38%, 1st quarter, 2020.

Performance Table Heading

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Performance Table Average Annual Total Returns (For the periods ended December 31, 2020)

Class B Shares | AB Dynamic Asset Allocation Portfolio | Class B

Risk/Return:

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Shareholder Fees (fees paid directly from your investment)

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Management Fees

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0.70%

Distribution (12b-1) Fees

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0.25%

Other Expenses: Transfer Agent

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none

^[1]

Other Expenses

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0.11%

Total Other Expenses

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0.11%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

Total Portfolio Operating Expenses

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1.07%

Fee Waiver and/or Expense Reimbursement

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(0.01%)

^[2]

Total Portfolio Operating Expenses After Fee Waiver and/or Expense Reimbursement

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1.06%

After 1 Year

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$ 108

After 3 Years

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339

After 5 Years

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589

After 10 Years

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$ 1,305

2011

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2012

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7.90%

2013

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12.04%

2014

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4.21%

2015

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(1.30%)

2016

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3.37%

2017

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14.32%

2018

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(7.35%)

2019

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15.24%

2020

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4.86%

Highest Quarterly Return, Label

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Best Quarter

Highest Quarterly Return, Date

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Dec. 31, 2020

Highest Quarterly Return

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8.23%

Lowest Quarterly Return, Label

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Worst Quarter

Lowest Quarterly Return, Date

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Mar. 31, 2020

Lowest Quarterly Return

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(11.38%)

1 Year

rr_AverageAnnualReturnYear01

4.86%

5 Years

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5.76%

Since Inception

rr_AverageAnnualReturnSinceInception

4.95%

^[3]

Inception Date

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Apr. 01, 2011

Class B Shares | AB Dynamic Asset Allocation Portfolio | MSCI World Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

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1 Year

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15.90%

5 Years

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12.19%

Since Inception

rr_AverageAnnualReturnSinceInception

9.54%

^[3]

Class B Shares | AB Dynamic Asset Allocation Portfolio | Bloomberg Barclays U.S. Treasury Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

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1 Year

rr_AverageAnnualReturnYear01

8.00%

^[4]

5 Years

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3.77%

^[4]

Since Inception

rr_AverageAnnualReturnSinceInception

3.44%

^[3],[4]

[1]	Amount is less than .01%.
[2]	In connection with the Portfolio’s investments in AB Government Money Market Portfolio (the “Money Market Portfolio”) (except for the investment of any cash collateral from securities lending), the Adviser has contractually agreed to waive its management fee from the Portfolio and/or reimburse other expenses of the Portfolio in an amount equal to the Portfolio’s pro rata share of the Money Market Portfolio’s effective management fee, as included in “Acquired Fund Fees and Expenses”. The agreement will remain in effect until May 1, 2022 and may only be terminated or changed with the consent of the Portfolio’s Board of Directors. In addition, the agreement will be automatically extended for one-year terms unless the Adviser provides notice of termination to the Portfolio at least 60 days prior to the end of the period.
[3]	Since inception return is from April 1, 2011.
[4]	The information for the Bloomberg Barclays U.S. Treasury Index and for the composite index is presented to show how the Portfolio’s performance compares with the returns of indices of securities similar to those in which the Portfolio invests.