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

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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 33% of the average value of its portfolio.

Portfolio Turnover, Rate

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33.00%

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 equity securities of a limited number of large, carefully selected, high-quality U.S. companies. The Portfolio invests primarily in the domestic equity securities of companies selected by the Adviser for their growth potential within various market sectors. The Portfolio emphasizes investments in large, seasoned companies. Under normal circumstances, the Portfolio invests at least 80% of its net assets in common stocks of large-capitalization companies.

For these purposes, “large-capitalization companies” are those that, at the time of investment, have market capitalizations within the range of market capitalizations of companies appearing in the Russell 1000

Growth Index. While the market capitalizations of companies in the Russell 1000

Growth Index ranged from approximately $0.6 billion to $2.3 trillion as of December 31, 2020, the Portfolio normally invests in common stocks of companies with market capitalizations of at least $5 billion at the time of purchase.

The Adviser expects that normally the Portfolio’s portfolio will tend to emphasize investments in securities issued by U.S. companies, although it may invest in foreign securities.

The Adviser allocates the Portfolio’s investments among broad sector groups based on the fundamental company research conducted by the Adviser’s internal research staff, assessing the current and forecasted investment opportunities and conditions, as well as diversification and risk considerations. The Adviser may vary the percentage allocations among market sectors and may change the market sectors in which the Portfolio invests as companies’ potential for growth within a sector matures and new trends for growth emerge.

The Adviser’s research focus is on companies with high sustainable growth prospects, high or improving return on invested capital, transparent business models, and strong and lasting competitive advantages.

The Portfolio may, at times, invest in shares of exchange-traded funds, or ETFs, in lieu of making direct investments in securities. ETFs may provide more efficient and economical exposure to the types of companies and geographic locations in which the Portfolio seeks to invest than direct investments.

The Portfolio may enter into 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, futures contracts (including futures contracts on individual securities and stock indices) or shares of ETFs. 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), 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.

•

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.

•

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.

•

Industry/Sector Risk:

Investments in a particular sector, industry or group of related industries, such as the information technology or health care sector, may have more risk because market or economic factors affecting that sector or industry could have a significant effect on the value of the Portfolio’s investments.

•

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

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 25.81%, 2nd quarter, 2020; and Worst Quarter was down -15.85%, 3rd quarter, 2011.

Performance Table Heading

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

Class B Shares | AB Large Cap 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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0.60%

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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0.07%

Total Other Expenses

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0.07%

Acquired Fund Fees and Expenses

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0.01%

Total Portfolio Operating Expenses

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0.93%

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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0.92%

After 1 Year

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$ 94

After 3 Years

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295

After 5 Years

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514

After 10 Years

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$ 1,142

2011

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(3.27%)

2012

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16.12%

2013

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37.00%

2014

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13.84%

2015

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10.86%

2016

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2.36%

2017

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31.67%

2018

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2.32%

2019

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34.37%

2020

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35.15%

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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25.81%

Lowest Quarterly Return, Label

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Worst Quarter

Lowest Quarterly Return, Date

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Sep. 30, 2011

Lowest Quarterly Return

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(15.85%)

1 Year

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35.15%

5 Years

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20.15%

10 Years

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17.14%

Class B Shares | AB Large Cap Growth Portfolio | Russell 1000® Growth Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

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1 Year

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38.49%

5 Years

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21.00%

10 Years

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17.21%

[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.