This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Portfolio. The table and Examples below do 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 in the Annual Portfolio Operating Expenses table and Examples 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, 2023

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 25% of the average value of its portfolio.

Portfolio Turnover, Rate

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25.00%

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 primarily in a focused international portfolio of equity securities of companies whose business activities the Adviser believes position the company to benefit from certain sustainable investment themes that align with one or more of the United Nations Sustainable Development Goals (“SDGs”). These themes principally include the advancement of climate, health and empowerment. Under normal circumstances, the Portfolio invests at least 80% of its net assets in equity securities of issuers

located outside of the United States that satisfy the Portfolio’s sustainable thematic criteria and in derivative instruments related to such securities. An issuer that derives at least 25% of its total revenues from activities consistent with the achievement of the SDGs meets such criteria, although many of the issuers in which the Portfolio invests will derive a much greater portion of their revenues from such activities.

The Adviser employs a combination of “top‑down” and “bottom‑up” investment processes with the goal of identifying, based on its internal research and analysis, securities of companies worldwide that fit into sustainable investment themes. First, the Adviser identifies through its “top‑down” process the sustainable investment themes. In addition to this “top‑down” thematic approach, the Adviser then uses a “bottom‑up” analysis of individual companies that focuses on prospective earnings growth, valuation, and quality of company management and on evaluating a company’s risks, including those related to environmental, social and corporate governance (“ESG”) factors. ESG factors, which can vary across companies and industries, may include environmental impact, corporate governance, ethical business practices, diversity and employee practices, product safety, supply chain management and community impact. Eligible investments include securities of issuers that the Adviser believes will maximize total return while also contributing to positive societal impact aligned with one or more SDGs. While the Adviser emphasizes focusing on individual companies with favorable ESG attributes over the use of broad-based negative screens (e.g., disqualifying business activities) in assessing a company’s exposure to ESG factors, the Portfolio will not invest in companies that derive revenue from direct involvement in alcohol, coal, gambling, pornography, prisons, tobacco or weapons.

The Adviser normally considers a large universe of mid‑ to large-capitalization companies worldwide for investment, but may invest in companies of any size. The Portfolio invests, under normal circumstances, in the equity securities of companies located in at least three countries (and normally substantially more) other than the United States. The Portfolio invests in securities of companies in both developed and emerging market countries, with the stock selection process determining the geographic distribution of the Portfolio’s investments. The Portfolio also invests in the equity securities of companies located in the United States with exposure to international markets. The Portfolio may sell securities that no longer meet the investment criteria described above.

Currency exposures can have a dramatic impact on equity returns, significantly adding to returns in some years and greatly diminishing them in others. The Adviser may seek to hedge the currency exposure resulting from a securities position when it finds the currency exposure unattractive. To hedge all or a portion of its currency risk, the Portfolio may, from time to time, invest in currency-related derivatives, including forward currency exchange contracts, futures contracts, options on futures contracts, swaps and options. Decisions regarding portfolio investments and whether or not to hedge foreign currency exposures are evaluated separately by the Adviser.

The Portfolio may enter into other derivatives transactions, such as options, futures contracts, forwards, and swaps. The Portfolio may use options strategies involving the purchase and/or writing of various combinations of call and/or put options, including on individual securities and stock indices or futures contracts (including futures contracts on individual securities and stock indices). These transactions may be used, for example, in an effort to earn extra income, to adjust exposure to individual securities or markets, or to protect all or a portion of the Portfolio’s portfolio from a decline in value, sometimes within certain ranges.

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) and regional and global conflicts, that affect large portions of the market. It includes the risk that a particular style of investing, such as the Portfolio’s growth approach, may underperform the market generally.

•

Focused Portfolio Risk: Investments in a limited number of companies may have more risk because changes in the value of a single security may have a more significant effect, either negative or positive, on the Portfolio’s net asset value, or NAV, than would be the case if the Portfolio were invested in a larger number of companies.

•

Sector Risk: The Portfolio may have more risk than a more diversified portfolio because it may invest to a significant extent in one or more particular market sectors, such as the information technology or financial services sector. To the extent it does so, market or economic factors affecting the relevant sector(s) could have a major effect on the value of the Portfolio’s investments.

•

ESG Risk: Applying ESG and sustainability criteria to the investment process may exclude securities of certain issuers for non‑investment reasons and, therefore, the Portfolio may forgo some market opportunities available to funds that do not use ESG or sustainability criteria. Securities of companies with ESG practices may shift into and out of favor depending on market and economic conditions, and the Portfolio’s performance may at times be better or worse than the performance of funds that do not use ESG or sustainability criteria. Furthermore, “sustainability” is not a uniformly defined characteristic, and the Portfolio’s sustainability criteria may differ from those used by other funds. In addition, in evaluating an investment, the investment adviser is dependent upon information and data that may be incomplete, inaccurate or unavailable, which could adversely affect the analysis of the ESG and sustainability factors relevant to a particular investment.

•

Foreign (Non-U.S.) Risk: 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.

•

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.

•

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, which is the risk that the counterparty (the party on the other side of the transaction) on a derivative transaction will be unable or unwilling to honor its contractual obligations to the Portfolio.

•

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 ten years; and

•

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

Performance Additional Market Index [Text]

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The information for the MSCI World Index (ex. U.S.) is presented to show how the Portfolio’s performance compares with the returns of an index 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 23.85%, 2nd quarter, 2020; and Worst Quarter was down -19.05%, 1st quarter, 2020.

Performance Table Heading

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Performance Table Average Annual Total Returns (For the periods ended December 31, 2021)

Class B Shares | AB International Growth 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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0.75%

Distribution (12b-1) Fees

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0.25%

Other Expenses: Transfer Agent

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0.01%

Other Expenses

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0.52%

Total Other Expenses

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0.53%

Total Portfolio Operating Expenses

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1.53%

Fee Waiver and/or Expense Reimbursement

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(0.05%)

^[1]

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

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1.48%

After 1 Year

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$ 151

After 3 Years

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478

After 5 Years

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829

After 10 Years

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$ 1,819

2012

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15.23%

2013

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13.32%

2014

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(1.41%)

2015

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(2.17%)

2016

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(7.07%)

2017

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34.63%

2018

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(17.60%)

2019

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27.23%

2020

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29.60%

2021

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8.01%

Highest Quarterly Return, Label

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Best Quarter

Highest Quarterly Return, Date

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Jun. 30, 2020

Highest Quarterly Return

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23.85%

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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(19.05%)

1 Year

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8.01%

5 Years

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14.59%

10 Years

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8.74%

Class B Shares | AB International Growth Portfolio | MSCI AC World Index (ex. U.S.) (reflects no deduction for fees, expenses, or taxes except the reinvestment of dividends net of non-U.S. withholding taxes)

Risk/Return:

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1 Year

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7.82%

5 Years

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9.61%

10 Years

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7.28%

Class B Shares | AB International Growth Portfolio | MSCI World Index (ex. U.S.) (reflects no deduction for fees, expenses, or taxes except the reinvestment of dividends net of non-U.S. withholding taxes)

Risk/Return:

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1 Year

rr_AverageAnnualReturnYear01

12.62%

^[2]

5 Years

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9.63%

^[2]

10 Years

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7.84%

^[2]

[1]

The Adviser has contractually agreed to waive its management fee and/or to bear expenses of the Portfolio in order to reduce total Portfolio operating expenses, on an annualized basis, by .05% of the Portfolio’s average daily net assets. The fee waiver and/or expense reimbursement agreement will remain in effect until May 1, 2023 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.

[2]