Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	ALLIANCEBERNSTEIN CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Nov. 01, 2013
AllianceBernstein Small Cap Growth Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	ALLIANCEBERNSTEIN SMALL CAP GROWTH PORTFOLIO EFFECTIVE FEBRUARY 1, 2013, THE FUND IS CLOSED TO NEW INVESTORS EXCEPT AS DESCRIBED BELOW. CURRENT SHAREHOLDERS AS OF JANUARY 31, 2013, MAY CONTINUE TO PURCHASE ADDITIONAL FUND SHARES, INCLUDING THROUGH REINVESTMENT OF DIVIDENDS AND CAPITAL GAINS DISTRIBUTIONS AND EXCHANGES. IN ADDITION, THE FOLLOWING CATEGORIES OF SHAREHOLDERS AND INVESTORS MAY CONTINUE TO PURCHASE FUND SHARES: (I) INVESTORS THAT ENTERED INTO A LETTER OF INTENT PRIOR TO JANUARY 31, 2013; (II) PARTICIPANTS IN GROUP RETIREMENT PLANS THAT OFFERED SHARES OF THE FUND AS AN INVESTMENT OPTION AS OF JANUARY 31, 2013; (III) WRAP FEE PROGRAMS OR FINANCIAL INTERMEDIARIES CHARGING ASSET-BASED FEES THAT PURCHASE SHARES ON BEHALF OF CLIENTS IN EXISTING ACCOUNTS HOLDING SHARES OF THE FUND AS OF JANUARY 31, 2013; AND (IV) CUSTOMERS OF CERTAIN OTHER FINANCIAL INTERMEDIARIES AS APPROVED BY THE ADVISER.
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund’s investment objective is long-term growth of capital.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge reductions if you and members of your family invest, or agree to invest in the future, at least $100,000 in AllianceBernstein Mutual Funds. More information about these and other discounts is available from your financial intermediary and in Investing in the Funds--Sales Charge Reduction Programs for Class A Shares on page 45 of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 108 of the Funds’ SAI.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	SHAREHOLDER FEES (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund 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 and may result in higher taxes when Fund shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Fund Operating Expenses or in the Examples, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 76% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	76.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Purchases of Class A shares in amounts of $1,000,000 or more, or by certain group retirement plans, may be subject to a 1%, 1-year CDSC, which may be subject to waiver in certain circumstances. Class B shares automatically convert to Class A shares after eight years. The CDSC decreases over time. For Class B shares the CDSC decreases 1.00% annually to 0% after the fourth year. For Class C shares the CDSC is 0% after the first year.
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge reductions if you and members of your family invest, or agree to invest in the future, at least $100,000 in AllianceBernstein Mutual Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 100,000
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLES
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The Examples are intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Fund 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 and that the Fund’s operating expenses stay the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text]	rr_ExpenseExampleNoRedemptionByYearCaption	For the share classes listed below, you would pay the following expenses if you did not redeem your shares at the end of the period:
Strategy [Heading]	rr_StrategyHeading	PRINCIPAL STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests primarily in a diversified portfolio of equity securities with relatively smaller capitalizations as compared to the overall U.S. market. Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities of smaller companies. For these purposes, "smaller companies" are those that, at the time of investment, fall within the lowest 20% of the total U.S. equity market capitalization (excluding, for purposes of this calculation, companies with market capitalizations of less than $10 million). As of June 30, 2013, there were approximately 4,168 smaller companies, and those smaller companies had market capitalizations ranging up to approximately $9.96 billion. Because the Fund's definition of smaller companies is dynamic, the limits on market capitalization will change with the markets. The Fund may invest in any company and industry and in any type of equity security with potential for capital appreciation. It invests in well-known and established companies and in new and less-seasoned companies. The Fund's investment policies emphasize investments in companies that are demonstrating improving financial results and a favorable earnings outlook. The Fund may invest in foreign securities. When selecting securities, the Adviser typically looks for companies that have strong, experienced management teams, strong market positions, and the potential to support greater than expected earnings growth rates. In making specific investment decisions for the Fund, the Adviser combines fundamental and quantitative analysis in its stock selection process. The Fund may periodically invest in the securities of companies that are expected to appreciate due to a development particularly or uniquely applicable to that company regardless of general business conditions or movements of the market as a whole. The Fund invests primarily in equity securities but may also invest in other types of securities, such as preferred stocks. The Fund may, at times, invest in shares of 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 Fund seeks to invest than direct investments. The Fund may also invest up to 20% of its total assets in rights or warrants. The Fund may enter into derivatives transactions, such as options, futures contracts, forwards, and swaps. The Fund 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 Fund's portfolio from a decline in value, sometimes within certain ranges.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Fund'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 that affect large portions of the market. It includes the risk that a particular style of investing, such as growth, may underperform the market generally. CAPITALIZATION RISK: Investments in small- and mid-capitalization companies may be more volatile than investments in large-capitalization companies. Investments in small-capitalization companies may have additional risks because these companies have limited product lines, markets or financial resources. 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 less liquid due to adverse market, economic, political, regulatory or other factors. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Fund, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Fund 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 Fund, but there is no guarantee that its techniques will produce the intended results. As with all investments, you may lose money by investing in the Fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Fund.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	BAR CHART AND PERFORMANCE INFORMATION
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance information provide an indication of the historical risk of an investment in the Fund by showing: how the Fund’s performance changed from year to year over ten years; and how the Fund’s average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Fund’s website at www.AllianceBernstein.com (click on “Individuals--U.S.” then “Products & Performance”). The Fund’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	how the Fund’s performance changed from year to year over ten years; and how the Fund’s average annual returns for one, five and ten years compare to those of a broad-based securities market index.
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.AllianceBernstein.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	BAR CHART
Bar Chart Narrative [Text Block]	rr_BarChartNarrativeTextBlock	The annual returns in the bar chart are for the Fund’s Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through September 30, 2013, the year-to-date unannualized return for Class A shares was 33.52%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Fund’s Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the period shown in the bar chart, the Fund’s: BEST QUARTER WAS UP 21.22%, 2ND QUARTER, 2009; AND WORST QUARTER WAS DOWN -28.82%, 4TH QUARTER, 2008.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE AVERAGE ANNUAL TOTAL RETURNS (For the periods ended December 31, 2012)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	Are an estimate, which is based on the highest historical individual federal marginal income tax rates, and do not reflect the impact of state and local taxes;
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Are not relevant to investors who hold fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns: -Are shown for Class A shares only and will vary for the other Classes of shares because these Classes have different expense ratios;
AllianceBernstein Small Cap Growth Portfolio | CLASS A SHARES
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.25%
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none	[1]
Exchange Fee	rr_ExchangeFee	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.27%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.25%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.07%
Total Other Expenses	rr_OtherExpensesOverAssets	0.32%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.34%
After 1 Year	rr_ExpenseExampleYear01	556
After 3 Years	rr_ExpenseExampleYear03	831
After 5 Years	rr_ExpenseExampleYear05	1,128
After 10 Years	rr_ExpenseExampleYear10	1,969
2003	rr_AnnualReturn2003	48.09%
2004	rr_AnnualReturn2004	13.95%
2005	rr_AnnualReturn2005	4.71%
2006	rr_AnnualReturn2006	10.58%
2007	rr_AnnualReturn2007	13.97%
2008	rr_AnnualReturn2008	(45.14%)
2009	rr_AnnualReturn2009	42.02%
2010	rr_AnnualReturn2010	37.00%
2011	rr_AnnualReturn2011	4.13%
2012	rr_AnnualReturn2012	15.03%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	33.52%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	21.22%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(28.82%)
1 YEAR	rr_AverageAnnualReturnYear01	10.14%	[2]
5 YEARS	rr_AverageAnnualReturnYear05	4.13%	[2]
10 YEARS	rr_AverageAnnualReturnYear10	10.55%	[2]
AllianceBernstein Small Cap Growth Portfolio | CLASS B SHARES
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees Column [Text]	rr_ShareholderFeesColumnName	(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	4.00%	[3]
Exchange Fee	rr_ExchangeFee	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.31%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.37%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.12%
After 1 Year	rr_ExpenseExampleYear01	615
After 3 Years	rr_ExpenseExampleYear03	864
After 5 Years	rr_ExpenseExampleYear05	1,139
After 10 Years	rr_ExpenseExampleYear10	2,253
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	215
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	664
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,139
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,253
1 YEAR	rr_AverageAnnualReturnYear01	10.09%
5 YEARS	rr_AverageAnnualReturnYear05	4.15%
10 YEARS	rr_AverageAnnualReturnYear10	10.29%
AllianceBernstein Small Cap Growth Portfolio | CLASS C SHARES
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	1.00%	[4]
Exchange Fee	rr_ExchangeFee	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.26%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.07%
Total Other Expenses	rr_OtherExpensesOverAssets	0.33%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.08%
After 1 Year	rr_ExpenseExampleYear01	311
After 3 Years	rr_ExpenseExampleYear03	652
After 5 Years	rr_ExpenseExampleYear05	1,119
After 10 Years	rr_ExpenseExampleYear10	2,410
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	211
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	652
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,119
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	2,410
1 YEAR	rr_AverageAnnualReturnYear01	13.13%
5 YEARS	rr_AverageAnnualReturnYear05	4.22%
10 YEARS	rr_AverageAnnualReturnYear10	10.18%
AllianceBernstein Small Cap Growth Portfolio | ADVISOR CLASS SHARES
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Exchange Fee	rr_ExchangeFee	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.26%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.32%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.07%
After 1 Year	rr_ExpenseExampleYear01	109
After 3 Years	rr_ExpenseExampleYear03	340
After 5 Years	rr_ExpenseExampleYear05	590
After 10 Years	rr_ExpenseExampleYear10	1,306
1 YEAR	rr_AverageAnnualReturnYear01	15.34%
5 YEARS	rr_AverageAnnualReturnYear05	5.32%
10 YEARS	rr_AverageAnnualReturnYear10	11.33%
AllianceBernstein Small Cap Growth Portfolio | CLASS R SHARES
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Exchange Fee	rr_ExchangeFee	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.24%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.30%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.55%
After 1 Year	rr_ExpenseExampleYear01	158
After 3 Years	rr_ExpenseExampleYear03	490
After 5 Years	rr_ExpenseExampleYear05	845
After 10 Years	rr_ExpenseExampleYear10	1,845
1 YEAR	rr_AverageAnnualReturnYear01	14.66%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	4.89%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	10.89%	[5]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Mar. 01, 2005	[5]
AllianceBernstein Small Cap Growth Portfolio | CLASS K SHARES
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Exchange Fee	rr_ExchangeFee	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.15%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.21%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.21%
After 1 Year	rr_ExpenseExampleYear01	123
After 3 Years	rr_ExpenseExampleYear03	384
After 5 Years	rr_ExpenseExampleYear05	665
After 10 Years	rr_ExpenseExampleYear10	1,466
1 YEAR	rr_AverageAnnualReturnYear01	15.08%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	5.20%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	11.20%	[5]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Mar. 01, 2005	[5]
AllianceBernstein Small Cap Growth Portfolio | CLASS I SHARES
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Exchange Fee	rr_ExchangeFee	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.11%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.17%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.92%
After 1 Year	rr_ExpenseExampleYear01	94
After 3 Years	rr_ExpenseExampleYear03	293
After 5 Years	rr_ExpenseExampleYear05	509
After 10 Years	rr_ExpenseExampleYear10	$ 1,131
1 YEAR	rr_AverageAnnualReturnYear01	15.42%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	5.55%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	11.56%	[5]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Mar. 01, 2005	[5]
AllianceBernstein Small Cap Growth Portfolio | Return After Taxes on Distributions | CLASS A SHARES
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	9.59%	[2]
5 YEARS	rr_AverageAnnualReturnYear05	3.95%	[2]
10 YEARS	rr_AverageAnnualReturnYear10	10.46%	[2]
AllianceBernstein Small Cap Growth Portfolio | Return After Taxes on Distributions and Sale of Fund Shares | CLASS A SHARES
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	7.31%	[2]
5 YEARS	rr_AverageAnnualReturnYear05	3.51%	[2]
10 YEARS	rr_AverageAnnualReturnYear10	9.43%	[2]
AllianceBernstein Small Cap Growth Portfolio | Russell 2000(R) Growth Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	14.59%
5 YEARS	rr_AverageAnnualReturnYear05	3.49%
10 YEARS	rr_AverageAnnualReturnYear10	9.80%

[1] Purchases of Class A shares in amounts of $1,000,000 or more, or by certain group retirement plans, may be subject to a 1%, 1-year CDSC, which may be subject to waiver in certain circumstances.

[2] After-tax returns: -Are shown for Class A shares only and will vary for the other Classes of shares because these Classes have different expense ratios; -Are an estimate, which is based on the highest historical individual federal marginal income tax rates, and do not reflect the impact of state and local taxes; actual after-tax returns depend on an individual investor's tax situation and are likely to differ from those shown; and -Are not relevant to investors who hold fund shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[3] Class B shares automatically convert to Class A shares after eight years. The CDSC decreases over time. For Class B shares the CDSC decreases 1.00% annually to 0% after the fourth year.

[4] For Class C shares the CDSC is 0% after the first year.

[5] Inception date for Class R, Class K and Class I shares: 3/1/05. Performance information for periods prior to the inception of Class R, Class K and Class I shares is the performance of the Fund's Class A shares adjusted to reflect the higher expense ratio of the Class R shares and the lower expense ratios of Class K and Class I shares, respectively.