485BPOS

As filed with the Securities and Exchange Commission on November 7, 2018

File Nos. 002-29901

811-01716

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933
Pre-Effective Amendment No.	☐
Post-Effective Amendment No. 261	☒

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940

Amendment No. 240 ☒

AB CAP FUND, INC.

(Exact Name of Registrant as Specified in Charter)

1345 Avenue of the Americas

New York, New York 10105

(Address of Principal Executive Office) (Zip Code)

Registrant’s Telephone Number, including Area Code:

(800) 221-5672

Emilie D. Wrapp

AllianceBernstein L.P.

1345 Avenue of the Americas

New York, New York 10105

(Name and address of agent for service)

Copies of communications to:

Paul M. Miller

Seward & Kissel LLP

901 K Street, NW

Suite 800

Washington, DC 20001

It is proposed that this filing will become effective (check appropriate box):

☒ immediately upon filing pursuant to paragraph (b)

☐ on (date) pursuant to paragraph (b)

☐ 60 days after filing pursuant to paragraph (a)(1)

☐ on (date) pursuant to paragraph (a)(1)

☐ 75 days after filing pursuant to paragraph (a)(2)

☐ on (date) pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

☐ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

This Post-Effective Amendment No. 261 relates solely to the Class A, Class B, Class C, Advisor Class, Class R, Class K, Class I and Class Z shares of the AB Small Cap Growth Portfolio, the Class A, Class C, Advisor Class, Class R, Class K, Class I and Class Z shares of the AB Concentrated Growth Fund, the Class A, Class C and Advisor Class shares of the AB Global Core Equity Portfolio, the Class A, Class C, Advisor Class, Class R, Class K and Class I shares of the AB Select US Equity Portfolio, the Class A, Class C, Advisor Class, Class R, Class K and Class I shares of the AB Select US Long/Short Portfolio, the Class A, Class C, and Advisor Class of the AB International Strategic Core Portfolio, and the Class A, Class C and Advisor Class shares of the AB Concentrated International Growth Portfolio. No information in the Registrant’s Registration Statement relating to the other Series or Classes of the Registrant not included herein is amended or superseded.

SIGNATURE

Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this Amendment to its Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Amendment to its Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City and State of New York, on the 7^th day of November, 2018.

AB CAP FUND, INC.
By:	Robert M. Keith*
	Robert M. Keith President

Pursuant to the requirements of the Securities Act of l933, as amended, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated:

	Signature	Title	Date
(1)	Principal Executive Officer:
	Robert M. Keith * Robert M. Keith	President and Chief Executive Officer	November 7, 2018
(2)	Principal Financial and Accounting Officer:
	/s/    Joseph J. Mantineo Joseph J. Mantineo	Treasurer and Chief Financial Officer	November 7, 2018
(3)	All of the Directors:
	Michael J. Downey* William H. Foulk, Jr.* Nancy P. Jacklin* Robert M. Keith* Carol C. McMullen* Garry L. Moody* Marshall C. Turner, Jr.* Earl D. Weiner*
*By:	/s/    Stephen J. Laffey Stephen J. Laffey (Attorney-in-fact)		November 7, 2018

Index to Exhibits

Exhibit No.	Description of Exhibits
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CALC	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Oct. 26, 2018
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Central Index Key	dei_EntityCentralIndexKey	0000081443
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Oct. 26, 2018
Document Effective Date	dei_DocumentEffectiveDate	Oct. 31, 2018
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
Entity Inv Company Type	dei_EntityInvCompanyType	N-1A

XML

AB Concentrated Growth Fund

AB CONCENTRATED GROWTH FUND

INVESTMENT OBJECTIVE

The Fund’s investment objective is long-term growth of capital.

FEES AND EXPENSES OF THE FUND

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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI").

You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB Concentrated Growth Fund	CLASS A SHARES		CLASS C SHARES		ADVISOR CLASS SHARES	CLASS R SHARES	CLASS K SHARES	CLASS I SHARES	CLASS Z SHARES
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.25%		none		none	none	none	none	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	[1]	1.00%	[2]	none	none	none	none	none
Exchange Fee	none		none		none	none	none	none	none

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage <br/>of the value of your investment)

Annual Fund Operating Expenses - AB Concentrated Growth Fund		CLASS A	CLASS C	ADVISOR CLASS		CLASS R		CLASS K		CLASS I	CLASS Z
Management Fees		0.80%	0.80%	0.80%		0.80%		0.80%		0.80%	0.80%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	none		0.50%		0.25%		none	none
Other Expenses: Transfer Agent		0.05%	0.05%	0.05%		0.06%		0.05%		0.02%	0.02%
Other Expenses		0.11%	0.11%	0.11%		0.09%		0.12%		0.14%	0.10%
Total Other Expenses		0.16%	0.16%	0.16%		0.15%		0.17%		0.16%	0.12%
Acquired Fund Fees and Expenses		0.01%	0.01%	none	[1]	none	[1]	none	[1]	0.01%	0.01%
Total Annual Fund Operating Expenses		1.22%	1.97%	0.96%		1.45%		1.22%		0.97%	0.93%
Fee Waiver and/or Expense Reimbursement	[2]	(0.01%)	(0.01%)	none	[1]	none	[1]	none	[1]	(0.01%)	(0.01%)
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement		1.21%	1.96%	0.96%		1.45%		1.22%		0.96%	0.92%

EXAMPLES

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, that the Fund’s operating expenses stay the same and that any fee waiver remains in effect for only the first year. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - AB Concentrated Growth Fund - USD ($)	CLASS A	CLASS C		ADVISOR CLASS	CLASS R	CLASS K	CLASS I	CLASS Z
After 1 Year	$ 543	$ 299	[1]	$ 98	$ 148	$ 124	$ 98	$ 94
After 3 Years	795	617		306	459	387	308	295
After 5 Years	1,066	1,061		531	792	670	535	514
After 10 Years	$ 1,839	$ 2,295		$ 1,178	$ 1,735	$ 1,477	$ 1,189	$ 1,142

PORTFOLIO TURNOVER

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 period, the Fund's portfolio turnover rate was 27% of the average value of its portfolio.

PRINCIPAL STRATEGIES

The Adviser seeks to achieve the Fund’s investment objective of long-term growth of capital by investing primarily in common stocks of listed U.S. companies. The Adviser employs an appraisal method that attempts to measure each prospective company’s quality and growth rate by numerous factors. Such factors include: a company’s record and projections of profit and earnings growth, accuracy and availability of information with respect to the company, success and experience of management, accessibility of management to the Fund’s Adviser, product lines and competitive position both in the United States and abroad, lack of cyclicality, large market capitalization and liquidity of the company’s securities. The Adviser compares these results to the general stock markets to determine the relative attractiveness of each company at a given time. The Adviser weighs economic, political and market factors in making investment decisions; this appraisal technique attempts to measure each investment candidate not only against other stocks of the same industry group, but also against a broad spectrum of investments. While the Fund primarily invests in companies that have market capitalizations of $5 billion or more, it may invest in companies that have market capitalizations of $3 billion to $5 billion.

The Fund invests in a relatively small number of individual stocks. The Fund is considered to be “non-diversified”, which means that the securities laws do not limit the percentage of its assets that it may invest in any one company (subject to certain limitations under the Internal Revenue Code of 1986, as amended (the “Code”)).

PRINCIPAL RISKS

• MARKET RISK: The value of the Fund's assets will fluctuate as the equity markets fluctuate. The value of the Fund's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market.

• 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 Fund's net asset value, or NAV.

• SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's investments.

• CAPITALIZATION RISK: Investments in mid-capitalization companies may be more volatile and less liquid than investments in large-capitalization companies.

• NON-DIVERSIFICATION RISK: The Fund may have more risk because it is "non-diversified", meaning that it can invest more of its assets in a smaller number of issuers. Accordingly, changes in the value of a single security may have a more significant effect, either negative or positive, on the Fund's NAV.

• 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.

BAR CHART AND PERFORMANCE INFORMATION

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.abfunds.com (click on “Investments--Mutual Funds”).

The Fund’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.

The information shown below reflects the historical performance of the W.P. Stewart & Co. Growth Fund and that fund’s predecessor (together the “Predecessor Fund”) prior to the reorganization of the Predecessor Fund into Advisor Class shares of the Fund on February 28, 2014. The Predecessor Fund and the Fund have substantially similar investment strategies and the same portfolio management team.

BAR CHART

The annual returns in the bar chart are for the Predecessor Fund’s shares for periods prior to its reorganization into Advisor Class shares of the Fund. Through September 30, 2018, the year-to-date unannualized return for Advisor Class shares was 15.88%.

During the period shown in the bar chart, the Fund's:

BEST QUARTER WAS UP 17.10%, 1ST QUARTER, 2012; AND WORST QUARTER WAS DOWN
-20.33%, 4TH QUARTER, 2008.

PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns - AB Concentrated Growth Fund		1 YEAR	5 YEARS	10 YEARS	INCEPTION DATE
CLASS A	[1],[2]	17.50%	13.90%	8.60%	Feb. 28, 2014
CLASS A | Return After Taxes on Distributions	[1],[2]	16.55%	13.24%	8.19%	Feb. 28, 2014
CLASS A | Return After Taxes on Distributions and Sale of Fund Shares	[1],[2]	10.69%	11.05%	6.95%	Feb. 28, 2014
CLASS C	[2]	20.80%	14.05%	8.25%	Feb. 28, 2014
ADVISOR CLASS		23.01%	15.17%	9.32%
CLASS R	[2]	22.41%	14.61%	8.76%	Feb. 28, 2014
CLASS K	[2]	22.66%	14.90%	9.07%	Feb. 28, 2014
CLASS I	[2]	22.97%	15.19%	9.33%	Feb. 28, 2014
CLASS Z	[2]	23.02%	15.19%	9.33%	Feb. 28, 2014
S&P 500(R) Index (reflects no deduction for fees, expenses, or taxes)		21.83%	15.79%	8.50%

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[1] Amount is less than .005%.

[2] In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[1] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

[1] 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.

[2] Inception date for Class A, Class C, Class R, Class K, Class I and Class Z shares: 2/28/14. Performance information for periods prior to the inception of Class A, Class C, Class R, Class K, Class I and Class Z shares is the performance of the Fund’s Advisor Class shares adjusted to reflect the respective expense ratios of the Class A, Class C, Class R, Class K, Class I and Class Z shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
AB Concentrated Growth Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB CONCENTRATED GROWTH FUND
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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI"). You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.
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 <br/>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 period, the Fund's portfolio turnover rate was 27% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	27.00%
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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances. For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.
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 AB 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, that the Fund’s operating expenses stay the same and that any fee waiver remains 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]	rr_StrategyHeading	PRINCIPAL STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Adviser seeks to achieve the Fund’s investment objective of long-term growth of capital by investing primarily in common stocks of listed U.S. companies. The Adviser employs an appraisal method that attempts to measure each prospective company’s quality and growth rate by numerous factors. Such factors include: a company’s record and projections of profit and earnings growth, accuracy and availability of information with respect to the company, success and experience of management, accessibility of management to the Fund’s Adviser, product lines and competitive position both in the United States and abroad, lack of cyclicality, large market capitalization and liquidity of the company’s securities. The Adviser compares these results to the general stock markets to determine the relative attractiveness of each company at a given time. The Adviser weighs economic, political and market factors in making investment decisions; this appraisal technique attempts to measure each investment candidate not only against other stocks of the same industry group, but also against a broad spectrum of investments. While the Fund primarily invests in companies that have market capitalizations of $5 billion or more, it may invest in companies that have market capitalizations of $3 billion to $5 billion. The Fund invests in a relatively small number of individual stocks. The Fund is considered to be “non-diversified”, which means that the securities laws do not limit the percentage of its assets that it may invest in any one company (subject to certain limitations under the Internal Revenue Code of 1986, as amended (the “Code”)).
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 equity markets fluctuate. The value of the Fund's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. 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 Fund's net asset value, or NAV. SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's investments. CAPITALIZATION RISK: Investments in mid-capitalization companies may be more volatile and less liquid than investments in large-capitalization companies. NON-DIVERSIFICATION RISK: The Fund may have more risk because it is "non-diversified", meaning that it can invest more of its assets in a smaller number of issuers. Accordingly, changes in the value of a single security may have a more significant effect, either negative or positive, on the Fund's NAV. 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.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	<ul type="square"><li>NON-DIVERSIFICATION RISK: The Fund may have more risk because it is "non-diversified", meaning that it can invest more of its assets in a smaller number of issuers. Accordingly, changes in the value of a single security may have a more significant effect, either negative or positive, on the Fund's NAV.</li></ul>
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.abfunds.com (click on “Investments--Mutual Funds”). The Fund’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future. The information shown below reflects the historical performance of the W.P. Stewart & Co. Growth Fund and that fund’s predecessor (together the “Predecessor Fund”) prior to the reorganization of the Predecessor Fund into Advisor Class shares of the Fund on February 28, 2014. The Predecessor Fund and the Fund have substantially similar investment strategies and the same portfolio management team.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	<ul type="square"><li>how the Fund’s performance changed from year to year over ten years; and</li></ul><ul type="square"><li>how the Fund’s average annual returns for one, five and ten years compare to those of a broad-based securities market index.</li></ul>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.abfunds.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 Predecessor Fund’s shares for periods prior to its reorganization into Advisor Class shares of the Fund. Through September 30, 2018, the year-to-date unannualized return for Advisor Class shares was 15.88%.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the period shown in the bar chart, the Fund's: BEST QUARTER WAS UP 17.10%, 1ST QUARTER, 2012; AND WORST QUARTER WAS DOWN -20.33%, 4TH QUARTER, 2008.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns: -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	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.
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;
AB Concentrated Growth Fund | CLASS A
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.11%
Total Other Expenses	rr_OtherExpensesOverAssets	0.16%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.22%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.21%
After 1 Year	rr_ExpenseExampleYear01	$ 543
After 3 Years	rr_ExpenseExampleYear03	795
After 5 Years	rr_ExpenseExampleYear05	1,066
After 10 Years	rr_ExpenseExampleYear10	$ 1,839
1 YEAR	rr_AverageAnnualReturnYear01	17.50%	[3],[4]
5 YEARS	rr_AverageAnnualReturnYear05	13.90%	[3],[4]
10 YEARS	rr_AverageAnnualReturnYear10	8.60%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2014	[3],[4]
AB Concentrated Growth Fund | CLASS C
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%	[5]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.11%
Total Other Expenses	rr_OtherExpensesOverAssets	0.16%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.97%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.96%
After 1 Year	rr_ExpenseExampleYear01	$ 299	[6]
After 3 Years	rr_ExpenseExampleYear03	617
After 5 Years	rr_ExpenseExampleYear05	1,061
After 10 Years	rr_ExpenseExampleYear10	$ 2,295
1 YEAR	rr_AverageAnnualReturnYear01	20.80%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	14.05%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	8.25%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2014	[4]
AB Concentrated Growth Fund | ADVISOR CLASS
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.11%
Total Other Expenses	rr_OtherExpensesOverAssets	0.16%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	none	[7]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.96%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	none	[2],[7]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.96%
After 1 Year	rr_ExpenseExampleYear01	$ 98
After 3 Years	rr_ExpenseExampleYear03	306
After 5 Years	rr_ExpenseExampleYear05	531
After 10 Years	rr_ExpenseExampleYear10	$ 1,178
2008	rr_AnnualReturn2008	(31.06%)
2009	rr_AnnualReturn2009	32.64%
2010	rr_AnnualReturn2010	12.60%
2011	rr_AnnualReturn2011	0.81%
2012	rr_AnnualReturn2012	15.87%
2013	rr_AnnualReturn2013	36.44%
2014	rr_AnnualReturn2014	13.09%
2015	rr_AnnualReturn2015	1.32%
2016	rr_AnnualReturn2016	5.36%
2017	rr_AnnualReturn2017	23.01%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	15.88%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2012
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	17.10%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(20.33%)
1 YEAR	rr_AverageAnnualReturnYear01	23.01%
5 YEARS	rr_AverageAnnualReturnYear05	15.17%
10 YEARS	rr_AverageAnnualReturnYear10	9.32%
AB Concentrated Growth Fund | CLASS R
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.06%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.09%
Total Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	none	[7]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.45%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	none	[2],[7]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.45%
After 1 Year	rr_ExpenseExampleYear01	$ 148
After 3 Years	rr_ExpenseExampleYear03	459
After 5 Years	rr_ExpenseExampleYear05	792
After 10 Years	rr_ExpenseExampleYear10	$ 1,735
1 YEAR	rr_AverageAnnualReturnYear01	22.41%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	14.61%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	8.76%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2014	[4]
AB Concentrated Growth Fund | CLASS K
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.12%
Total Other Expenses	rr_OtherExpensesOverAssets	0.17%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	none	[7]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.22%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	none	[2],[7]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.22%
After 1 Year	rr_ExpenseExampleYear01	$ 124
After 3 Years	rr_ExpenseExampleYear03	387
After 5 Years	rr_ExpenseExampleYear05	670
After 10 Years	rr_ExpenseExampleYear10	$ 1,477
1 YEAR	rr_AverageAnnualReturnYear01	22.66%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	14.90%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	9.07%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2014	[4]
AB Concentrated Growth Fund | CLASS I
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.02%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.14%
Total Other Expenses	rr_OtherExpensesOverAssets	0.16%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.97%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.96%
After 1 Year	rr_ExpenseExampleYear01	$ 98
After 3 Years	rr_ExpenseExampleYear03	308
After 5 Years	rr_ExpenseExampleYear05	535
After 10 Years	rr_ExpenseExampleYear10	$ 1,189
1 YEAR	rr_AverageAnnualReturnYear01	22.97%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	15.19%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	9.33%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2014	[4]
AB Concentrated Growth Fund | CLASS Z
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.80%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.02%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.10%
Total Other Expenses	rr_OtherExpensesOverAssets	0.12%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.93%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.92%
After 1 Year	rr_ExpenseExampleYear01	$ 94
After 3 Years	rr_ExpenseExampleYear03	295
After 5 Years	rr_ExpenseExampleYear05	514
After 10 Years	rr_ExpenseExampleYear10	$ 1,142
1 YEAR	rr_AverageAnnualReturnYear01	23.02%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	15.19%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	9.33%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2014	[4]
AB Concentrated Growth Fund | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	16.55%	[3],[4]
5 YEARS	rr_AverageAnnualReturnYear05	13.24%	[3],[4]
10 YEARS	rr_AverageAnnualReturnYear10	8.19%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2014	[3],[4]
AB Concentrated Growth Fund | Return After Taxes on Distributions and Sale of Fund Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	10.69%	[3],[4]
5 YEARS	rr_AverageAnnualReturnYear05	11.05%	[3],[4]
10 YEARS	rr_AverageAnnualReturnYear10	6.95%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2014	[3],[4]
AB Concentrated Growth Fund | S&P 500(R) Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	21.83%
5 YEARS	rr_AverageAnnualReturnYear05	15.79%
10 YEARS	rr_AverageAnnualReturnYear10	8.50%

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[3] 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.

[4] Inception date for Class A, Class C, Class R, Class K, Class I and Class Z shares: 2/28/14. Performance information for periods prior to the inception of Class A, Class C, Class R, Class K, Class I and Class Z shares is the performance of the Fund’s Advisor Class shares adjusted to reflect the respective expense ratios of the Class A, Class C, Class R, Class K, Class I and Class Z shares.

[5] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[6] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

[7] Amount is less than .005%.

XML

AB Small Cap Growth Portfolio

AB SMALL CAP GROWTH PORTFOLIO

INVESTMENT OBJECTIVE

The Fund’s investment objective is long-term growth of capital.

FEES AND EXPENSES OF THE FUND

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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI").

You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB Small Cap Growth Portfolio	CLASS A SHARES		CLASS B SHARES		CLASS C SHARES		ADVISOR CLASS SHARES	CLASS R SHARES	CLASS K SHARES	CLASS I SHARES	CLASS Z SHARES
Shareholder Fees Column [Text]			(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.25%		none		none		none	none	none	none	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	[1]	4.00%	[2]	1.00%	[3]	none	none	none	none	none
Exchange Fee	none		none		none		none	none	none	none	none

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage <br/>of the value of your investment)

Annual Fund Operating Expenses - AB Small Cap Growth Portfolio	CLASS A	CLASS B	CLASS C	ADVISOR CLASS	CLASS R	CLASS K	CLASS I	CLASS Z
Management Fees	0.75%	0.75%	0.75%	0.75%	0.75%	0.75%	0.75%	0.75%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	1.00%	none	0.50%	0.25%	none	none
Other Expenses: Transfer Agent	0.10%	0.15%	0.10%	0.10%	0.25%	0.06%	0.11%	0.02%
Other Expenses	0.04%	0.04%	0.04%	0.04%	0.04%	0.04%	0.04%	0.04%
Total Other Expenses	0.14%	0.19%	0.14%	0.14%	0.29%	0.10%	0.15%	0.06%
Acquired Fund Fees and Expenses	0.01%	0.01%	0.01%	0.01%	0.01%	0.01%	0.01%	0.01%
Total Annual Fund Operating Expenses	1.15%	1.95%	1.90%	0.90%	1.55%	1.11%	0.91%	0.82%

EXAMPLES

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 - AB Small Cap Growth Portfolio - USD ($)	CLASS A	CLASS B	CLASS C	ADVISOR CLASS	CLASS R	CLASS K	CLASS I	CLASS Z
After 1 Year	$ 537	$ 598	$ 293	$ 92	$ 158	$ 113	$ 93	$ 83
After 3 Years	775	812	597	287	490	353	290	261
After 5 Years	1,031	1,052	1,026	498	845	612	504	454
After 10 Years	$ 1,763	$ 2,067	$ 2,222	$ 1,108	$ 1,845	$ 1,352	$ 1,120	$ 1,013

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:

Expense Example, No Redemption - AB Small Cap Growth Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 198	$ 193
After 3 Years	612	597
After 5 Years	1,052	1,026
After 10 Years	$ 2,067	$ 2,222

PORTFOLIO TURNOVER

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 65% of the average value of its portfolio.

PRINCIPAL STRATEGIES

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, 2018, there were approximately 4,204 smaller companies, and those smaller companies had market capitalizations ranging up to approximately $13.4 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 exchange-traded funds ("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.

PRINCIPAL RISKS

• 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.

• SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's investments.

• 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.

BAR CHART AND PERFORMANCE INFORMATION

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.abfunds.com (click on "Investments--Mutual Funds").

The Fund’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.

BAR CHART

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, 2018, the year-to-date unannualized return for Class A shares was 27.70%.

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 <br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns - AB Small Cap Growth Portfolio		1 YEAR	5 YEARS	10 YEARS	INCEPTION DATE
CLASS A	[1]	28.88%	14.07%	9.46%
CLASS A | Return After Taxes on Distributions	[1]	26.05%	12.04%	8.39%
CLASS A | Return After Taxes on Distributions and Sale of Fund Shares	[1]	18.28%	10.90%	7.57%
CLASS B		29.56%	14.15%	9.21%
CLASS C		32.62%	14.21%	9.10%
ADVISOR CLASS		34.93%	15.36%	10.23%
CLASS R		34.09%	14.72%	9.70%
CLASS K		34.54%	15.10%	10.04%
CLASS I		34.91%	15.45%	10.39%
CLASS Z	[2]	35.03%	15.43%	10.25%	Jul. 01, 2015
Russell 2000(R) Growth Index (reflects no deduction for fees, expenses, or taxes)		22.17%	15.21%	9.19%

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] 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.

[3] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[1] 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.

[2] Inception date for Class Z shares: 7/1/15. Performance information for periods prior to the inception of Class Z shares is the performance of the Fund’s Class A shares adjusted to reflect the expense ratio of the Class Z shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
AB Small Cap Growth Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB SMALL CAP GROWTH PORTFOLIO
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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI"). You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.
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 <br/>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 65% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	65.00%
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 contingent deferred sales charge, or 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. Class C shares automatically convert to Class A shares after ten years.
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 AB 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, 2018, there were approximately 4,204 smaller companies, and those smaller companies had market capitalizations ranging up to approximately $13.4 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 exchange-traded funds ("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. SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's investments. 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.abfunds.com (click on "Investments--Mutual Funds"). 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	<ul type="square"><li>how the Fund’s performance changed from year to year over ten years; and</li></ul><ul type="square"><li>how the Fund’s average annual returns for one, five and ten years compare to those of a broad-based securities market index.</li></ul>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.abfunds.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, 2018, the year-to-date unannualized return for Class A shares was 27.70%.
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 <br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns: -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	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.
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;
AB Small Cap Growth Portfolio | CLASS A
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.10%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.04%
Total Other Expenses	rr_OtherExpensesOverAssets	0.14%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.15%
After 1 Year	rr_ExpenseExampleYear01	$ 537
After 3 Years	rr_ExpenseExampleYear03	775
After 5 Years	rr_ExpenseExampleYear05	1,031
After 10 Years	rr_ExpenseExampleYear10	$ 1,763
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%
2013	rr_AnnualReturn2013	45.11%
2014	rr_AnnualReturn2014	(1.76%)
2015	rr_AnnualReturn2015	(1.19%)
2016	rr_AnnualReturn2016	6.41%
2017	rr_AnnualReturn2017	34.60%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	27.70%
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	28.88%	[2]
5 YEARS	rr_AverageAnnualReturnYear05	14.07%	[2]
10 YEARS	rr_AverageAnnualReturnYear10	9.46%	[2]
AB Small Cap Growth Portfolio | CLASS B
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.15%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.04%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.95%
After 1 Year	rr_ExpenseExampleYear01	$ 598
After 3 Years	rr_ExpenseExampleYear03	812
After 5 Years	rr_ExpenseExampleYear05	1,052
After 10 Years	rr_ExpenseExampleYear10	2,067
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	198
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	612
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,052
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,067
1 YEAR	rr_AverageAnnualReturnYear01	29.56%
5 YEARS	rr_AverageAnnualReturnYear05	14.15%
10 YEARS	rr_AverageAnnualReturnYear10	9.21%
AB Small Cap Growth Portfolio | CLASS C
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.10%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.04%
Total Other Expenses	rr_OtherExpensesOverAssets	0.14%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.90%
After 1 Year	rr_ExpenseExampleYear01	$ 293
After 3 Years	rr_ExpenseExampleYear03	597
After 5 Years	rr_ExpenseExampleYear05	1,026
After 10 Years	rr_ExpenseExampleYear10	2,222
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	193
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	597
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,026
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,222
1 YEAR	rr_AverageAnnualReturnYear01	32.62%
5 YEARS	rr_AverageAnnualReturnYear05	14.21%
10 YEARS	rr_AverageAnnualReturnYear10	9.10%
AB Small Cap Growth Portfolio | ADVISOR CLASS
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.10%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.04%
Total Other Expenses	rr_OtherExpensesOverAssets	0.14%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.90%
After 1 Year	rr_ExpenseExampleYear01	$ 92
After 3 Years	rr_ExpenseExampleYear03	287
After 5 Years	rr_ExpenseExampleYear05	498
After 10 Years	rr_ExpenseExampleYear10	$ 1,108
1 YEAR	rr_AverageAnnualReturnYear01	34.93%
5 YEARS	rr_AverageAnnualReturnYear05	15.36%
10 YEARS	rr_AverageAnnualReturnYear10	10.23%
AB Small Cap Growth Portfolio | CLASS R
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.25%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.04%
Total Other Expenses	rr_OtherExpensesOverAssets	0.29%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
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	34.09%
5 YEARS	rr_AverageAnnualReturnYear05	14.72%
10 YEARS	rr_AverageAnnualReturnYear10	9.70%
AB Small Cap Growth Portfolio | CLASS K
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.06%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.04%
Total Other Expenses	rr_OtherExpensesOverAssets	0.10%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.11%
After 1 Year	rr_ExpenseExampleYear01	$ 113
After 3 Years	rr_ExpenseExampleYear03	353
After 5 Years	rr_ExpenseExampleYear05	612
After 10 Years	rr_ExpenseExampleYear10	$ 1,352
1 YEAR	rr_AverageAnnualReturnYear01	34.54%
5 YEARS	rr_AverageAnnualReturnYear05	15.10%
10 YEARS	rr_AverageAnnualReturnYear10	10.04%
AB Small Cap Growth Portfolio | CLASS I
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_ExchangeFeeOverRedemption	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	0.04%
Total Other Expenses	rr_OtherExpensesOverAssets	0.15%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.91%
After 1 Year	rr_ExpenseExampleYear01	$ 93
After 3 Years	rr_ExpenseExampleYear03	290
After 5 Years	rr_ExpenseExampleYear05	504
After 10 Years	rr_ExpenseExampleYear10	$ 1,120
1 YEAR	rr_AverageAnnualReturnYear01	34.91%
5 YEARS	rr_AverageAnnualReturnYear05	15.45%
10 YEARS	rr_AverageAnnualReturnYear10	10.39%
AB Small Cap Growth Portfolio | CLASS Z
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.02%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.04%
Total Other Expenses	rr_OtherExpensesOverAssets	0.06%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.82%
After 1 Year	rr_ExpenseExampleYear01	$ 83
After 3 Years	rr_ExpenseExampleYear03	261
After 5 Years	rr_ExpenseExampleYear05	454
After 10 Years	rr_ExpenseExampleYear10	$ 1,013
1 YEAR	rr_AverageAnnualReturnYear01	35.03%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	15.43%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	10.25%	[5]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jul. 01, 2015	[5]
AB Small Cap Growth Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	26.05%	[2]
5 YEARS	rr_AverageAnnualReturnYear05	12.04%	[2]
10 YEARS	rr_AverageAnnualReturnYear10	8.39%	[2]
AB Small Cap Growth Portfolio | Return After Taxes on Distributions and Sale of Fund Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	18.28%	[2]
5 YEARS	rr_AverageAnnualReturnYear05	10.90%	[2]
10 YEARS	rr_AverageAnnualReturnYear10	7.57%	[2]
AB 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	22.17%
5 YEARS	rr_AverageAnnualReturnYear05	15.21%
10 YEARS	rr_AverageAnnualReturnYear10	9.19%

[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 contingent deferred sales charge, or 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. Class C shares automatically convert to Class A shares after ten years.

[5] Inception date for Class Z shares: 7/1/15. Performance information for periods prior to the inception of Class Z shares is the performance of the Fund’s Class A shares adjusted to reflect the expense ratio of the Class Z shares.

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AB Select US Equity Portfolio

AB SELECT US EQUITY PORTFOLIO

INVESTMENT OBJECTIVE

The Fund’s investment objective is long-term growth of capital.

FEES AND EXPENSES OF THE FUND

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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI").

You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB Select US Equity Portfolio	CLASS A SHARES		CLASS C SHARES		ADVISOR CLASS SHARES	CLASS R SHARES	CLASS K SHARES	CLASS I SHARES
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.25%		none		none	none	none	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	[1]	1.00%	[2]	none	none	none	none
Exchange Fee	none		none		none	none	none	none

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage <br/>of the value of your investment)

Annual Fund Operating Expenses - AB Select US Equity Portfolio		CLASS A	CLASS C		ADVISOR CLASS	CLASS R		CLASS K		CLASS I
Management Fees		1.00%	1.00%		1.00%	1.00%		1.00%		1.00%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%		none	0.50%		0.25%		none
Other Expenses: Transfer Agent		0.03%	0.03%		0.03%	0.07%		0.20%		0.02%
Other Expenses		0.18%	0.18%		0.18%	0.19%		0.18%		0.20%
Total Other Expenses		0.21%	0.21%		0.21%	0.26%		0.38%		0.22%
Acquired Fund Fees and Expenses		0.02%	0.02%		0.02%	0.02%		0.02%		0.02%
Total Annual Fund Operating Expenses		1.48%	2.23%		1.23%	1.78%		1.65%		1.24%
Fee Waiver and/or Expense Reimbursement	[1]	(0.01%)	none	[2]	(0.01%)	none	[2]	(0.09%)	[3]	(0.01%)
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement		1.47%	2.23%		1.22%	1.78%		1.56%		1.23%

EXAMPLES

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, that the Fund’s operating expenses stay the same and that any fee waiver remains in effect for only the first year. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - AB Select US Equity Portfolio - USD ($)	CLASS A	CLASS C		ADVISOR CLASS	CLASS R	CLASS K	CLASS I
After 1 Year	$ 568	$ 326	[1]	$ 124	$ 181	$ 159	$ 125
After 3 Years	872	697		389	560	512	392
After 5 Years	1,198	1,195		675	964	888	680
After 10 Years	$ 2,117	$ 2,565		$ 1,488	$ 2,095	$ 1,947	$ 1,499

PORTFOLIO TURNOVER

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 236% of the average value of its portfolio.

PRINCIPAL STRATEGIES

Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities of U.S. companies. For purposes of this requirement, equity securities include common stock, preferred stock and derivatives related to common and preferred stocks.

The Adviser selects investments for the Fund through an intensive "bottom-up" approach that places an emphasis on companies that are engaged in business activities with solid long-term growth potential and operating in industries with high barriers to entry, that have strong cash flows and other financial metrics, and that have transparent financial statements and business models. The Adviser also evaluates the quality of company management based on a series of criteria, including: (1) management's focus on shareholder returns, such as through a demonstrated commitment to dividends and dividend growth, share buybacks or other shareholder-friendly corporate actions; (2) management's employment of conservative accounting methodologies; (3) management incentives, such as direct equity ownership; and (4) management accessibility. The Adviser seeks to identify companies where events or catalysts may drive the company's share price higher, such as earnings and/or revenue growth above consensus forecasts, potential market recognition of undervaluation or overstated market-risk discount, or the institution of shareholder-focused changes discussed in the preceding sentence. In light of this catalyst-focused approach, the Adviser expects to engage in active and frequent trading for the Fund. The Adviser may reduce or eliminate the Fund's holdings in a company's securities for a number of reasons, including if its evaluation of the above factors changes adversely, if the anticipated events or catalysts do not occur or do not affect the price of the securities as expected, or if the anticipated events or catalysts do occur and cause the securities to be, in the Adviser's view, overvalued or fully valued. At any given time the Fund may emphasize growth stocks over value stocks, or vice versa.

The Fund’s investments will be focused on securities of companies with large and medium market capitalizations, but it may also invest in securities of small-capitalization companies. The Fund may invest in non-U.S. companies, but will limit its investments in such companies to no more than 10% of its net assets. The Fund may purchase securities in initial public offerings and expects to do so on a regular basis.

PRINCIPAL RISKS

• MARKET RISK: The value of the Fund's assets will fluctuate as the stock, bond or currency markets fluctuate. The value of the Fund's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market.

• SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's investments.

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

• ACTIVE TRADING RISK: The Fund expects to engage in active and frequent trading of its portfolio securities and its portfolio turnover rate may greatly exceed 100%. A higher rate of portfolio turnover increases transaction costs, which may negatively affect the Fund's return. In addition, a high rate of portfolio turnover may result in substantial short-term gains, which may have adverse tax consequences for Fund shareholders.

• 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.

BAR CHART AND PERFORMANCE INFORMATION

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 the life of the Fund; and

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

You may obtain updated performance information on the Fund's website at www.abfunds.com (click on "Investments--Mutual Funds").

The Fund's past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.

BAR CHART

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, 2018, the year-to-date unannualized return for Class A shares was 10.06%.

During the period shown in the bar chart, the Fund's:

BEST QUARTER WAS UP 11.62%, 1ST QUARTER, 2012; AND WORST QUARTER WAS DOWN
-5.78%, 3RD QUARTER, 2015.

PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns - AB Select US Equity Portfolio		1 YEAR	5 YEARS	SINCE INCEPTION	[2]	INCEPTION DATE
CLASS A	[1]	17.00%	13.80%	14.49%		Dec. 08, 2011
CLASS A | Return After Taxes on Distributions	[1]	13.16%	11.43%	12.36%		Dec. 08, 2011
CLASS A | Return After Taxes on Distributions and Sale of Fund Shares	[1]	10.76%	10.12%	10.90%		Dec. 08, 2011
CLASS C		20.33%	13.94%	14.46%		Dec. 08, 2011
ADVISOR CLASS		22.48%	15.08%	15.62%		Dec. 08, 2011
CLASS R		21.77%	14.47%	15.00%		Dec. 08, 2011
CLASS K		22.05%	14.69%	15.23%		Dec. 08, 2011
CLASS I		22.56%	15.09%	15.61%		Dec. 08, 2011
S&P 500(R) Index (reflects no deduction for fees, expenses or taxes)		21.83%	15.79%	16.01%

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[1] In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[2] Amount is less than .005%.

[3] The fee waiver and/or expense reimbursement agreement will remain in effect until October 31, 2019 and will be automatically extended for one-year terms unless the Adviser provides notice of termination at least 60 days prior to the end of the period.

[1] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

[1] 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.

[2] Inception date for all Classes: 12/8/11.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
AB Select US Equity Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB SELECT US EQUITY PORTFOLIO
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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI"). You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.
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 <br/>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 236% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	236.00%
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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances. For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.
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 AB 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, that the Fund’s operating expenses stay the same and that any fee waiver remains 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]	rr_StrategyHeading	PRINCIPAL STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities of U.S. companies. For purposes of this requirement, equity securities include common stock, preferred stock and derivatives related to common and preferred stocks. The Adviser selects investments for the Fund through an intensive "bottom-up" approach that places an emphasis on companies that are engaged in business activities with solid long-term growth potential and operating in industries with high barriers to entry, that have strong cash flows and other financial metrics, and that have transparent financial statements and business models. The Adviser also evaluates the quality of company management based on a series of criteria, including: (1) management's focus on shareholder returns, such as through a demonstrated commitment to dividends and dividend growth, share buybacks or other shareholder-friendly corporate actions; (2) management's employment of conservative accounting methodologies; (3) management incentives, such as direct equity ownership; and (4) management accessibility. The Adviser seeks to identify companies where events or catalysts may drive the company's share price higher, such as earnings and/or revenue growth above consensus forecasts, potential market recognition of undervaluation or overstated market-risk discount, or the institution of shareholder-focused changes discussed in the preceding sentence. In light of this catalyst-focused approach, the Adviser expects to engage in active and frequent trading for the Fund. The Adviser may reduce or eliminate the Fund's holdings in a company's securities for a number of reasons, including if its evaluation of the above factors changes adversely, if the anticipated events or catalysts do not occur or do not affect the price of the securities as expected, or if the anticipated events or catalysts do occur and cause the securities to be, in the Adviser's view, overvalued or fully valued. At any given time the Fund may emphasize growth stocks over value stocks, or vice versa. The Fund’s investments will be focused on securities of companies with large and medium market capitalizations, but it may also invest in securities of small-capitalization companies. The Fund may invest in non-U.S. companies, but will limit its investments in such companies to no more than 10% of its net assets. The Fund may purchase securities in initial public offerings and expects to do so on a regular basis.
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, bond or currency markets fluctuate. The value of the Fund's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's investments. CAPITALIZATION RISK: Investments in small- and mid-capitalization companies may be more volatile than investments in large-capitalization companies. Investments in these companies may have additional risks because these companies may have limited product lines, markets or financial resources. ACTIVE TRADING RISK: The Fund expects to engage in active and frequent trading of its portfolio securities and its portfolio turnover rate may greatly exceed 100%. A higher rate of portfolio turnover increases transaction costs, which may negatively affect the Fund's return. In addition, a high rate of portfolio turnover may result in substantial short-term gains, which may have adverse tax consequences for Fund shareholders. 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 the life of the Fund; and how the Fund's average annual returns for one year, five years and since inception compare to those of a broad-based securities market index. You may obtain updated performance information on the Fund's website at www.abfunds.com (click on "Investments--Mutual Funds"). 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	<ul type="square"><li>how the Fund's performance changed from year to year over the life of the Fund; and</li></ul><ul type="square"><li>how the Fund's average annual returns for one year, five years and since inception compare to those of a broad-based securities market index.</li></ul>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.abfunds.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, 2018, the year-to-date unannualized return for Class A shares was 10.06%.
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 11.62%, 1ST QUARTER, 2012; AND WORST QUARTER WAS DOWN -5.78%, 3RD QUARTER, 2015.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns: -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	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.
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;
AB Select US Equity Portfolio | CLASS A
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.18%
Total Other Expenses	rr_OtherExpensesOverAssets	0.21%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.48%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.47%
After 1 Year	rr_ExpenseExampleYear01	$ 568
After 3 Years	rr_ExpenseExampleYear03	872
After 5 Years	rr_ExpenseExampleYear05	1,198
After 10 Years	rr_ExpenseExampleYear10	$ 2,117
2008	rr_AnnualReturn2008
2009	rr_AnnualReturn2009
2010	rr_AnnualReturn2010
2011	rr_AnnualReturn2011
2012	rr_AnnualReturn2012	16.21%
2013	rr_AnnualReturn2013	30.80%
2014	rr_AnnualReturn2014	12.76%
2015	rr_AnnualReturn2015	1.18%
2016	rr_AnnualReturn2016	9.24%
2017	rr_AnnualReturn2017	22.22%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	10.06%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2012
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	11.62%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(5.78%)
1 YEAR	rr_AverageAnnualReturnYear01	17.00%	[3]
5 YEARS	rr_AverageAnnualReturnYear05	13.80%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	14.49%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 08, 2011	[3]
AB Select US Equity Portfolio | CLASS C
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%	[5]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.18%
Total Other Expenses	rr_OtherExpensesOverAssets	0.21%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.23%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	none	[2],[6]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	2.23%
After 1 Year	rr_ExpenseExampleYear01	$ 326	[7]
After 3 Years	rr_ExpenseExampleYear03	697
After 5 Years	rr_ExpenseExampleYear05	1,195
After 10 Years	rr_ExpenseExampleYear10	$ 2,565
1 YEAR	rr_AverageAnnualReturnYear01	20.33%
5 YEARS	rr_AverageAnnualReturnYear05	13.94%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	14.46%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 08, 2011
AB Select US Equity Portfolio | ADVISOR CLASS
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.18%
Total Other Expenses	rr_OtherExpensesOverAssets	0.21%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.23%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.22%
After 1 Year	rr_ExpenseExampleYear01	$ 124
After 3 Years	rr_ExpenseExampleYear03	389
After 5 Years	rr_ExpenseExampleYear05	675
After 10 Years	rr_ExpenseExampleYear10	$ 1,488
1 YEAR	rr_AverageAnnualReturnYear01	22.48%
5 YEARS	rr_AverageAnnualReturnYear05	15.08%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	15.62%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 08, 2011
AB Select US Equity Portfolio | CLASS R
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.07%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.19%
Total Other Expenses	rr_OtherExpensesOverAssets	0.26%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.78%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	none	[2],[6]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.78%
After 1 Year	rr_ExpenseExampleYear01	$ 181
After 3 Years	rr_ExpenseExampleYear03	560
After 5 Years	rr_ExpenseExampleYear05	964
After 10 Years	rr_ExpenseExampleYear10	$ 2,095
1 YEAR	rr_AverageAnnualReturnYear01	21.77%
5 YEARS	rr_AverageAnnualReturnYear05	14.47%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	15.00%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 08, 2011
AB Select US Equity Portfolio | CLASS K
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.20%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.18%
Total Other Expenses	rr_OtherExpensesOverAssets	0.38%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.65%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.09%)	[2],[8]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.56%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	October 31, 2019
After 1 Year	rr_ExpenseExampleYear01	$ 159
After 3 Years	rr_ExpenseExampleYear03	512
After 5 Years	rr_ExpenseExampleYear05	888
After 10 Years	rr_ExpenseExampleYear10	$ 1,947
1 YEAR	rr_AverageAnnualReturnYear01	22.05%
5 YEARS	rr_AverageAnnualReturnYear05	14.69%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	15.23%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 08, 2011
AB Select US Equity Portfolio | CLASS I
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.02%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.20%
Total Other Expenses	rr_OtherExpensesOverAssets	0.22%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.02%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.24%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.23%
After 1 Year	rr_ExpenseExampleYear01	$ 125
After 3 Years	rr_ExpenseExampleYear03	392
After 5 Years	rr_ExpenseExampleYear05	680
After 10 Years	rr_ExpenseExampleYear10	$ 1,499
1 YEAR	rr_AverageAnnualReturnYear01	22.56%
5 YEARS	rr_AverageAnnualReturnYear05	15.09%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	15.61%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 08, 2011
AB Select US Equity Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	13.16%	[3]
5 YEARS	rr_AverageAnnualReturnYear05	11.43%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	12.36%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 08, 2011	[3]
AB Select US Equity Portfolio | Return After Taxes on Distributions and Sale of Fund Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	10.76%	[3]
5 YEARS	rr_AverageAnnualReturnYear05	10.12%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	10.90%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 08, 2011	[3]
AB Select US Equity Portfolio | S&P 500(R) Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	21.83%
5 YEARS	rr_AverageAnnualReturnYear05	15.79%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	16.01%	[4]

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[3] 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.

[4] Inception date for all Classes: 12/8/11.

[5] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[6] Amount is less than .005%.

[7] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

[8] The fee waiver and/or expense reimbursement agreement will remain in effect until October 31, 2019 and will be automatically extended for one-year terms unless the Adviser provides notice of termination at least 60 days prior to the end of the period.

XML

AB Select US Long/Short Portfolio

AB SELECT US LONG/SHORT PORTFOLIO

INVESTMENT OBJECTIVE

The Fund’s investment objective is long-term growth of capital.

FEES AND EXPENSES OF THE FUND

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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund’s Statement of Additional Information (“SAI”).

You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB Select US Long/Short Portfolio	CLASS A SHARES		CLASS C SHARES		ADVISOR CLASS SHARES	CLASS R SHARES	CLASS K SHARES	CLASS I SHARES
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.25%		none		none	none	none	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	[1]	1.00%	[2]	none	none	none	none
Exchange Fee	none		none		none	none	none	none

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage <br/>of the value of your investment)

Annual Fund Operating Expenses - AB Select US Long/Short Portfolio		CLASS A	CLASS C	ADVISOR CLASS	CLASS R		CLASS K		CLASS I
Management Fees		1.50%	1.50%	1.50%	1.50%		1.50%		1.50%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	none	0.50%		0.25%		none
Other Expenses: Transfer Agent		0.07%	0.07%	0.07%	0.26%		0.20%		0.02%
Dividend Expense, Borrowing Costs and Brokerage Expense on Securities Sold Short		0.06%	0.06%	0.06%	0.06%		0.06%		0.06%
Other Expenses		0.06%	0.06%	0.06%	0.06%		0.04%		0.06%
Total Other Expenses		0.19%	0.19%	0.19%	0.38%		0.30%		0.14%
Acquired Fund Fees and Expenses		0.07%	0.07%	0.07%	0.07%		0.07%		0.07%
Total Annual Fund Operating Expenses		2.01%	2.76%	1.76%	2.45%		2.12%		1.71%
Fee Waiver and/or Expense Reimbursement	[1]	(0.06%)	(0.06%)	(0.05%)	(0.23%)	[2]	(0.15%)	[2]	(0.06%)
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement		1.95%	2.70%	1.71%	2.22%		1.97%		1.65%

EXAMPLES

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, that the Fund's operating expenses stay the same and that any fee waiver remains in effect for only the first year. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - AB Select US Long/Short Portfolio - USD ($)	CLASS A	CLASS C		ADVISOR CLASS	CLASS R	CLASS K	CLASS I
After 1 Year	$ 615	$ 373	[1]	$ 174	$ 225	$ 200	$ 168
After 3 Years	1,023	851		549	742	650	533
After 5 Years	1,457	1,454		949	1,285	1,125	923
After 10 Years	$ 2,659	$ 3,085		$ 2,069	$ 2,769	$ 2,440	$ 2,014

PORTFOLIO TURNOVER

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 346% of the average value of its portfolio.

PRINCIPAL STRATEGIES

Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities of U.S. companies, short positions in such securities, and cash and U.S. cash equivalents.

The Adviser selects investments for the Fund's long positions through an intensive "bottom-up" approach that places an emphasis on companies that are engaged in business activities with solid long-term growth potential and high barriers to entry, that have strong cash flows and other financial metrics, and that have transparent financial statements and business models. The Adviser also evaluates the quality of company management based on a series of criteria, including: (1) management's focus on shareholder returns, such as through a demonstrated commitment to dividends and dividend growth, share buybacks or other shareholder-friendly corporate actions; (2) management's employment of conservative accounting methodologies; (3) management incentives, such as direct equity ownership; and (4) management accessibility. The Adviser seeks to identify companies where events or catalysts may drive the company's share price higher, such as earnings and/or revenue growth above consensus forecasts, potential market recognition of undervaluation or overstated market-risk discount, or the institution of any of the shareholder-friendly practices discussed in the preceding sentence. In light of this catalyst-focused approach, the Adviser expects to engage in active and frequent trading for the Fund.

The Adviser may reduce or eliminate the Fund's holdings in a company's securities for a number of reasons, including if its evaluation of the above factors changes adversely, if the anticipated events or catalysts do not occur or do not affect the price of the securities as expected, or if the anticipated events or catalysts do occur and cause the securities to be, in the Adviser's view, overvalued or fully valued. At any given time the Fund may emphasize growth stocks over value stocks, or vice versa.

In determining securities to be sold short, the Adviser looks for companies facing near-term difficulties such as high valuations, quality of earnings issues, or weakness in demand due to economic factors or long-term issues such as changing technology or competitive concerns in their industries. The Fund may also sell securities of exchange-traded funds ("ETFs") short, including to hedge its exposure to specific market sectors or if it believes a specific sector or asset will decline in value. When the Fund sells securities short, it sells a stock that it does not own (but has borrowed) at its current market price in anticipation that the price of the stock will decline. To complete, or close out, the short sale transaction, the Fund buys the same stock in the market at a later date and returns it to the lender.

The Adviser derives the ratio between long and short positions for the Fund based on its bottom-up analysis supplemented with macro-economic and market analyses. Under normal market conditions, the net long exposure of the Fund (long exposure minus short exposure) will range between 30% and 70%. The Adviser seeks to minimize the variability of Fund returns through industry diversification as well as by managing long and short exposures and/or by holding a material level of cash and/or cash equivalents. For example, the Fund may hold long positions in equity securities with a value equal to 60% of its net assets and have short sale obligations equal to 15% of its net assets, resulting in 45% net long exposure. Assuming a 60% long exposure, 40% of Fund assets will be held in cash or cash equivalents, including cash and cash equivalents held to cover the Fund's short sale obligations. During periods of excessive market risk, the Adviser may reduce the net long exposure of the Fund. The Fund may at times hold long and short positions that in the aggregate exceed the value of its net assets (i.e., so that the Fund is effectively leveraged).

The Fund's investments will be focused on securities of companies with large and medium market capitalizations, but it may also take long and short positions in securities of small-capitalization companies. The Fund may invest in non-U.S. companies, but currently intends to limit its investments in such companies to no more than 10% of its net assets. The Fund may purchase securities in initial public offerings and expects to do so on a regular basis.

The Fund may enter into derivatives transactions, such as options, futures contracts, forwards, and swaps, as part of its investment strategies or for hedging or other risk management purposes. These transactions may be used, for example, as a means to take a short position in a security or sector without actually selling securities short.

PRINCIPAL RISKS

• MARKET RISK: The value of the Fund's assets will fluctuate as the stock, bond or currency markets fluctuate. The value of the Fund's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market.

• SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's investments.

• SHORT SALE RISK: Short sales involve the risk that the Fund will incur a loss by subsequently buying a security at a higher price than the price at which it sold the security. The amount of such loss is theoretically unlimited, as it will be based on the increase in value of the security sold short. In contrast, the risk of loss from a long position is limited to the Fund's investment in the security, because the price of the security cannot fall below zero. The Fund may not always be able to close out a short position on favorable terms.

• 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.

• LEVERAGE RISK: To the extent the Fund uses leveraging techniques, the value of its shares may be more volatile because leverage tends to exaggerate the effect of any increase or decrease in the value of the Fund's investments.

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

• ACTIVE TRADING RISK: The Fund expects to engage in active and frequent trading of its portfolio securities and its portfolio turnover rate is expected to greatly exceed 100%. A higher rate of portfolio turnover increases transaction costs, which may negatively affect the Fund's return. In addition, a high rate of portfolio turnover may result in substantial short-term gains, which may have adverse tax consequences for Fund shareholders.

• 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.

BAR CHART AND PERFORMANCE INFORMATION

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 the life of the Fund; and

• how the Fund's average annual returns for one and five years and since inception compare to those of a broad-based securities market index.

You may obtain updated performance information on the Fund's website at www.abfunds.com (click on "Investments--Mutual Funds").

The Fund's past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.

BAR CHART

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, 2018, the year-to-date unannualized return for Class A shares was 7.37%.

During the period shown in the bar chart, the Fund's:

BEST QUARTER WAS UP 6.70%, 4TH QUARTER, 2013; AND WORST QUARTER WAS DOWN
-4.50%, 3RD QUARTER, 2015.

PERFORMANCE TABLE <br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns - AB Select US Long/Short Portfolio		1 YEAR	5 YEARS	SINCE INCEPTION	[2]	INCEPTION DATE
CLASS A	[1]	7.53%	6.75%	6.69%		Dec. 12, 2012
CLASS A | Return After Taxes on Distributions	[1]	5.53%	5.57%	5.54%		Dec. 12, 2012
CLASS A | Return After Taxes on Distributions and Sale of Fund Shares	[1]	4.54%	4.75%	4.71%		Dec. 12, 2012
CLASS C		10.42%	6.90%	6.82%		Dec. 12, 2012
ADVISOR CLASS		12.55%	7.95%	7.88%		Dec. 12, 2012
CLASS R		12.05%	7.44%	7.36%		Dec. 12, 2012
CLASS K		12.25%	7.68%	7.62%		Dec. 12, 2012
CLASS I		12.61%	8.00%	7.93%		Dec. 12, 2012
S&P 500(R) Index (reflects no deduction for fees, expenses or taxes)		21.83%	15.79%	15.59%

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[1] In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until October 31, 2019 and will be automatically extended for one-year terms unless the Adviser provides notice of termination at least 60 days prior to the end of the period.

[1] If you did not redeem your shares at the end of the period, your expenses would decrease by approximately $100.

[1] 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.

[2] Inception date for all Classes: 12/12/12.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
AB Select US Long/Short Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB SELECT US LONG/SHORT PORTFOLIO
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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund’s Statement of Additional Information (“SAI”). You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.
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 <br/>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 346% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	346.00%
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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances. For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.
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 AB 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, that the Fund's operating expenses stay the same and that any fee waiver remains 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]	rr_StrategyHeading	PRINCIPAL STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities of U.S. companies, short positions in such securities, and cash and U.S. cash equivalents. The Adviser selects investments for the Fund's long positions through an intensive "bottom-up" approach that places an emphasis on companies that are engaged in business activities with solid long-term growth potential and high barriers to entry, that have strong cash flows and other financial metrics, and that have transparent financial statements and business models. The Adviser also evaluates the quality of company management based on a series of criteria, including: (1) management's focus on shareholder returns, such as through a demonstrated commitment to dividends and dividend growth, share buybacks or other shareholder-friendly corporate actions; (2) management's employment of conservative accounting methodologies; (3) management incentives, such as direct equity ownership; and (4) management accessibility. The Adviser seeks to identify companies where events or catalysts may drive the company's share price higher, such as earnings and/or revenue growth above consensus forecasts, potential market recognition of undervaluation or overstated market-risk discount, or the institution of any of the shareholder-friendly practices discussed in the preceding sentence. In light of this catalyst-focused approach, the Adviser expects to engage in active and frequent trading for the Fund. The Adviser may reduce or eliminate the Fund's holdings in a company's securities for a number of reasons, including if its evaluation of the above factors changes adversely, if the anticipated events or catalysts do not occur or do not affect the price of the securities as expected, or if the anticipated events or catalysts do occur and cause the securities to be, in the Adviser's view, overvalued or fully valued. At any given time the Fund may emphasize growth stocks over value stocks, or vice versa. In determining securities to be sold short, the Adviser looks for companies facing near-term difficulties such as high valuations, quality of earnings issues, or weakness in demand due to economic factors or long-term issues such as changing technology or competitive concerns in their industries. The Fund may also sell securities of exchange-traded funds ("ETFs") short, including to hedge its exposure to specific market sectors or if it believes a specific sector or asset will decline in value. When the Fund sells securities short, it sells a stock that it does not own (but has borrowed) at its current market price in anticipation that the price of the stock will decline. To complete, or close out, the short sale transaction, the Fund buys the same stock in the market at a later date and returns it to the lender. The Adviser derives the ratio between long and short positions for the Fund based on its bottom-up analysis supplemented with macro-economic and market analyses. Under normal market conditions, the net long exposure of the Fund (long exposure minus short exposure) will range between 30% and 70%. The Adviser seeks to minimize the variability of Fund returns through industry diversification as well as by managing long and short exposures and/or by holding a material level of cash and/or cash equivalents. For example, the Fund may hold long positions in equity securities with a value equal to 60% of its net assets and have short sale obligations equal to 15% of its net assets, resulting in 45% net long exposure. Assuming a 60% long exposure, 40% of Fund assets will be held in cash or cash equivalents, including cash and cash equivalents held to cover the Fund's short sale obligations. During periods of excessive market risk, the Adviser may reduce the net long exposure of the Fund. The Fund may at times hold long and short positions that in the aggregate exceed the value of its net assets (i.e., so that the Fund is effectively leveraged). The Fund's investments will be focused on securities of companies with large and medium market capitalizations, but it may also take long and short positions in securities of small-capitalization companies. The Fund may invest in non-U.S. companies, but currently intends to limit its investments in such companies to no more than 10% of its net assets. The Fund may purchase securities in initial public offerings and expects to do so on a regular basis. The Fund may enter into derivatives transactions, such as options, futures contracts, forwards, and swaps, as part of its investment strategies or for hedging or other risk management purposes. These transactions may be used, for example, as a means to take a short position in a security or sector without actually selling securities short.
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, bond or currency markets fluctuate. The value of the Fund's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's investments. SHORT SALE RISK: Short sales involve the risk that the Fund will incur a loss by subsequently buying a security at a higher price than the price at which it sold the security. The amount of such loss is theoretically unlimited, as it will be based on the increase in value of the security sold short. In contrast, the risk of loss from a long position is limited to the Fund's investment in the security, because the price of the security cannot fall below zero. The Fund may not always be able to close out a short position on favorable terms. 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. LEVERAGE RISK: To the extent the Fund uses leveraging techniques, the value of its shares may be more volatile because leverage tends to exaggerate the effect of any increase or decrease in the value of the Fund's investments. CAPITALIZATION RISK: Investments in small- and mid-capitalization companies may be more volatile than investments in large-capitalization companies. Investments in these companies may have additional risks because these companies may have limited product lines, markets or financial resources. ACTIVE TRADING RISK: The Fund expects to engage in active and frequent trading of its portfolio securities and its portfolio turnover rate is expected to greatly exceed 100%. A higher rate of portfolio turnover increases transaction costs, which may negatively affect the Fund's return. In addition, a high rate of portfolio turnover may result in substantial short-term gains, which may have adverse tax consequences for Fund shareholders. 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 the life of the Fund; and how the Fund's average annual returns for one and five years and since inception compare to those of a broad-based securities market index. You may obtain updated performance information on the Fund's website at www.abfunds.com (click on "Investments--Mutual Funds"). 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	<ul type="square"><li>how the Fund's performance changed from year to year over the life of the Fund; and</li></ul><ul type="square"><li>how the Fund's average annual returns for one and five years and since inception compare to those of a broad-based securities market index.</li></ul>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.abfunds.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, 2018, the year-to-date unannualized return for Class A shares was 7.37%.
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 6.70%, 4TH QUARTER, 2013; AND WORST QUARTER WAS DOWN -4.50%, 3RD QUARTER, 2015.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE <br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns: -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	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.
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;
AB Select US Long/Short Portfolio | CLASS A
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.07%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Dividend Expense, Borrowing Costs and Brokerage Expense on Securities Sold Short	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.01%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.95%
After 1 Year	rr_ExpenseExampleYear01	$ 615
After 3 Years	rr_ExpenseExampleYear03	1,023
After 5 Years	rr_ExpenseExampleYear05	1,457
After 10 Years	rr_ExpenseExampleYear10	$ 2,659
2008	rr_AnnualReturn2008
2009	rr_AnnualReturn2009
2010	rr_AnnualReturn2010
2011	rr_AnnualReturn2011
2012	rr_AnnualReturn2012
2013	rr_AnnualReturn2013	20.55%
2014	rr_AnnualReturn2014	3.27%
2015	rr_AnnualReturn2015	(1.03%)
2016	rr_AnnualReturn2016	4.61%
2017	rr_AnnualReturn2017	12.26%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	7.37%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2013
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.70%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.50%)
1 YEAR	rr_AverageAnnualReturnYear01	7.53%	[3]
5 YEARS	rr_AverageAnnualReturnYear05	6.75%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.69%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 12, 2012	[3]
AB Select US Long/Short Portfolio | CLASS C
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%	[5]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.07%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Dividend Expense, Borrowing Costs and Brokerage Expense on Securities Sold Short	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.76%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	2.70%
After 1 Year	rr_ExpenseExampleYear01	$ 373	[6]
After 3 Years	rr_ExpenseExampleYear03	851
After 5 Years	rr_ExpenseExampleYear05	1,454
After 10 Years	rr_ExpenseExampleYear10	$ 3,085
1 YEAR	rr_AverageAnnualReturnYear01	10.42%
5 YEARS	rr_AverageAnnualReturnYear05	6.90%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.82%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 12, 2012
AB Select US Long/Short Portfolio | ADVISOR CLASS
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.07%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Dividend Expense, Borrowing Costs and Brokerage Expense on Securities Sold Short	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.76%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.71%
After 1 Year	rr_ExpenseExampleYear01	$ 174
After 3 Years	rr_ExpenseExampleYear03	549
After 5 Years	rr_ExpenseExampleYear05	949
After 10 Years	rr_ExpenseExampleYear10	$ 2,069
1 YEAR	rr_AverageAnnualReturnYear01	12.55%
5 YEARS	rr_AverageAnnualReturnYear05	7.95%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	7.88%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 12, 2012
AB Select US Long/Short Portfolio | CLASS R
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.26%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Dividend Expense, Borrowing Costs and Brokerage Expense on Securities Sold Short	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.38%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.45%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.23%)	[2],[7]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	2.22%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	October 31, 2019
After 1 Year	rr_ExpenseExampleYear01	$ 225
After 3 Years	rr_ExpenseExampleYear03	742
After 5 Years	rr_ExpenseExampleYear05	1,285
After 10 Years	rr_ExpenseExampleYear10	$ 2,769
1 YEAR	rr_AverageAnnualReturnYear01	12.05%
5 YEARS	rr_AverageAnnualReturnYear05	7.44%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	7.36%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 12, 2012
AB Select US Long/Short Portfolio | CLASS K
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.20%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.04%
Dividend Expense, Borrowing Costs and Brokerage Expense on Securities Sold Short	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.30%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.12%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.15%)	[2],[7]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.97%
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	October 31, 2019
After 1 Year	rr_ExpenseExampleYear01	$ 200
After 3 Years	rr_ExpenseExampleYear03	650
After 5 Years	rr_ExpenseExampleYear05	1,125
After 10 Years	rr_ExpenseExampleYear10	$ 2,440
1 YEAR	rr_AverageAnnualReturnYear01	12.25%
5 YEARS	rr_AverageAnnualReturnYear05	7.68%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	7.62%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 12, 2012
AB Select US Long/Short Portfolio | CLASS I
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	1.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.02%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.06%
Dividend Expense, Borrowing Costs and Brokerage Expense on Securities Sold Short	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.14%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.71%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.65%
After 1 Year	rr_ExpenseExampleYear01	$ 168
After 3 Years	rr_ExpenseExampleYear03	533
After 5 Years	rr_ExpenseExampleYear05	923
After 10 Years	rr_ExpenseExampleYear10	$ 2,014
1 YEAR	rr_AverageAnnualReturnYear01	12.61%
5 YEARS	rr_AverageAnnualReturnYear05	8.00%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	7.93%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 12, 2012
AB Select US Long/Short Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.53%	[3]
5 YEARS	rr_AverageAnnualReturnYear05	5.57%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	5.54%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 12, 2012	[3]
AB Select US Long/Short Portfolio | Return After Taxes on Distributions and Sale of Fund Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	4.54%	[3]
5 YEARS	rr_AverageAnnualReturnYear05	4.75%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	4.71%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Dec. 12, 2012	[3]
AB Select US Long/Short Portfolio | S&P 500(R) Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	21.83%
5 YEARS	rr_AverageAnnualReturnYear05	15.79%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	15.59%	[4]

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[3] 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.

[4] Inception date for all Classes: 12/12/12.

[5] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[6] If you did not redeem your shares at the end of the period, your expenses would decrease by approximately $100.

[7] The fee waiver and/or expense reimbursement agreement will remain in effect until October 31, 2019 and will be automatically extended for one-year terms unless the Adviser provides notice of termination at least 60 days prior to the end of the period.

XML

AB Global Core Equity Portfolio

AB GLOBAL CORE EQUITY PORTFOLIO

INVESTMENT OBJECTIVE

The Fund’s investment objective is to seek long-term growth of capital.

FEES AND EXPENSES OF THE FUND

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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI").

You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB Global Core Equity Portfolio	CLASS A SHARES		CLASS C SHARES		ADVISOR CLASS SHARES
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.25%		none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	[1]	1.00%	[2]	none
Exchange Fee	none		none		none

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage <br/> of the value of your investment)

Annual Fund Operating Expenses - AB Global Core Equity Portfolio	CLASS A	CLASS C	ADVISOR CLASS
Management Fees	0.75%	0.75%	0.75%
Distribution and/or Service (12b-1) Fees	0.25%	1.00%	none
Other Expenses: Transfer Agent	0.02%	0.05%	0.02%
Other Expenses	0.13%	0.10%	0.13%
Total Other Expenses	0.15%	0.15%	0.15%
Total Annual Fund Operating Expenses	1.15%	1.90%	0.90%

EXAMPLES

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 - AB Global Core Equity Portfolio - USD ($)	CLASS A	CLASS C		ADVISOR CLASS
After 1 Year	$ 537	$ 293	[1]	$ 92
After 3 Years	775	597		287
After 5 Years	1,031	1,026		498
After 10 Years	$ 1,763	$ 2,222		$ 1,108

PORTFOLIO TURNOVER

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 45% of the average value of its portfolio.

PRINCIPAL STRATEGIES

The Fund invests primarily in a portfolio of equity securities of issuers from markets around the world. Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities, at least 40% of its net assets in securities of non-U.S. companies, and invests in companies in at least three countries (including the United States).

The Fund is principally comprised of companies considered by the Adviser to offer good prospects for attractive returns relative to the general stock market. The Adviser will seek companies that are attractively valued and have the ability to generate high and sustainable returns on invested capital. In addition to returns on invested capital, other criteria that the Adviser will consider include strong business fundamentals, capable management, prudent corporate governance, strong balance sheet, strong earnings power, high earnings quality, low downside risk, and substantial upside potential. In managing the Fund, the Adviser will not seek to have a bias towards any investment style, economic sector, country or company size. The Fund’s holdings of non-U.S. companies will frequently include companies located in emerging markets, and at times emerging market companies will make up a significant portion of the Fund.

Fluctuations in currency exchange rates can have a dramatic impact of the returns of equity securities. While the Adviser may hedge the foreign currency exposure resulting from the Fund’s security positions through the use of currency-related derivatives, it is not required to do so.

PRINCIPAL RISKS

• 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.

• 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. These risks may be heightened with respect to investments in emerging market countries, where there may be an increased amount of economic, political and social instability.

• EMERGING MARKET RISK: Investments in emerging market countries may have more risk because the markets are less developed and less liquid as well as being subject to increased economic, political, regulatory or other uncertainties.

• CURRENCY RISK: Fluctuations in currency exchange rates may negatively affect the value of the Fund's investments or reduce its returns.

• SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's 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.

BAR CHART AND PERFORMANCE INFORMATION

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 the life of the Fund; and

• how the Fund's average annual returns for one year and since inception compare to those of a broad-based securities market index.

You may obtain updated performance information on the Fund's website at www.abfunds.com (click on "Investments--Mutual Funds").

The Fund's past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.

BAR CHART

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, 2018, the year-to-date unannualized return for Class A shares was 5.61%.

During the period shown in the bar chart, the Fund's:

BEST QUARTER WAS UP 7.89%, 1ST QUARTER, 2017; AND WORST QUARTER WAS DOWN
-8.57%, 3RD QUARTER, 2015.

PERFORMANCE TABLE<br/> AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)

Average Annual Total Returns - AB Global Core Equity Portfolio		1 YEAR	SINCE INCEPTION	[2]	INCEPTION DATE
CLASS A	[1]	19.79%	7.55%		Nov. 12, 2014
CLASS A | Return After Taxes on Distributions	[1]	18.37%	6.93%		Nov. 12, 2014
CLASS A | Return After Taxes on Distributions and Sale of Fund Shares	[1]	12.01%	5.73%		Nov. 12, 2014
CLASS C		23.21%	8.19%		Nov. 12, 2014
ADVISOR CLASS		25.49%	9.28%		Nov. 12, 2014
MSCI ACWI Index (Net) (reflects no deduction for fees, expenses, or taxes except the reinvestment of dividends of non-U.S. withholding taxes)		23.97%	8.69%

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[1] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

[1] 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.

[2] Inception date for all Classes: 11/12/14.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
AB Global Core Equity Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB GLOBAL CORE EQUITY PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund’s investment objective is to seek 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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI"). You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.
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 <br/> 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 45% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	45.00%
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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances. For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.
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 AB 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:
Strategy [Heading]	rr_StrategyHeading	PRINCIPAL STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests primarily in a portfolio of equity securities of issuers from markets around the world. Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities, at least 40% of its net assets in securities of non-U.S. companies, and invests in companies in at least three countries (including the United States). The Fund is principally comprised of companies considered by the Adviser to offer good prospects for attractive returns relative to the general stock market. The Adviser will seek companies that are attractively valued and have the ability to generate high and sustainable returns on invested capital. In addition to returns on invested capital, other criteria that the Adviser will consider include strong business fundamentals, capable management, prudent corporate governance, strong balance sheet, strong earnings power, high earnings quality, low downside risk, and substantial upside potential. In managing the Fund, the Adviser will not seek to have a bias towards any investment style, economic sector, country or company size. The Fund’s holdings of non-U.S. companies will frequently include companies located in emerging markets, and at times emerging market companies will make up a significant portion of the Fund. Fluctuations in currency exchange rates can have a dramatic impact of the returns of equity securities. While the Adviser may hedge the foreign currency exposure resulting from the Fund’s security positions through the use of currency-related derivatives, it is not required to do so.
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. 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. These risks may be heightened with respect to investments in emerging market countries, where there may be an increased amount of economic, political and social instability. EMERGING MARKET RISK: Investments in emerging market countries may have more risk because the markets are less developed and less liquid as well as being subject to increased economic, political, regulatory or other uncertainties. CURRENCY RISK: Fluctuations in currency exchange rates may negatively affect the value of the Fund's investments or reduce its returns. SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund's 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 the life of the Fund; and how the Fund's average annual returns for one year and since inception compare to those of a broad-based securities market index. You may obtain updated performance information on the Fund's website at www.abfunds.com (click on "Investments--Mutual Funds"). 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	<ul type="square"><li>how the Fund's performance changed from year to year over the life of the Fund; and</li></ul><ul type="square"><li>how the Fund's average annual returns for one year and since inception compare to those of a broad-based securities market index.</li></ul>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.abfunds.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, 2018, the year-to-date unannualized return for Class A shares was 5.61%.
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 7.89%, 1ST QUARTER, 2017; AND WORST QUARTER WAS DOWN -8.57%, 3RD QUARTER, 2015.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/> AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the periods ended December 31, 2017)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns: -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	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.
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;
AB Global Core Equity Portfolio | CLASS A
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.02%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.13%
Total Other Expenses	rr_OtherExpensesOverAssets	0.15%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.15%
After 1 Year	rr_ExpenseExampleYear01	$ 537
After 3 Years	rr_ExpenseExampleYear03	775
After 5 Years	rr_ExpenseExampleYear05	1,031
After 10 Years	rr_ExpenseExampleYear10	$ 1,763
2008	rr_AnnualReturn2008
2009	rr_AnnualReturn2009
2010	rr_AnnualReturn2010
2011	rr_AnnualReturn2011
2012	rr_AnnualReturn2012
2013	rr_AnnualReturn2013
2014	rr_AnnualReturn2014
2015	rr_AnnualReturn2015	(2.77%)
2016	rr_AnnualReturn2016	7.75%
2017	rr_AnnualReturn2017	25.16%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	5.61%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2017
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	7.89%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(8.57%)
1 YEAR	rr_AverageAnnualReturnYear01	19.79%	[2]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	7.55%	[2],[3]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Nov. 12, 2014	[2]
AB Global Core Equity Portfolio | CLASS C
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.10%
Total Other Expenses	rr_OtherExpensesOverAssets	0.15%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.90%
After 1 Year	rr_ExpenseExampleYear01	$ 293	[5]
After 3 Years	rr_ExpenseExampleYear03	597
After 5 Years	rr_ExpenseExampleYear05	1,026
After 10 Years	rr_ExpenseExampleYear10	$ 2,222
1 YEAR	rr_AverageAnnualReturnYear01	23.21%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	8.19%	[3]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Nov. 12, 2014
AB Global Core Equity Portfolio | ADVISOR CLASS
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.02%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.13%
Total Other Expenses	rr_OtherExpensesOverAssets	0.15%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.90%
After 1 Year	rr_ExpenseExampleYear01	$ 92
After 3 Years	rr_ExpenseExampleYear03	287
After 5 Years	rr_ExpenseExampleYear05	498
After 10 Years	rr_ExpenseExampleYear10	$ 1,108
1 YEAR	rr_AverageAnnualReturnYear01	25.49%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	9.28%	[3]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Nov. 12, 2014
AB Global Core Equity Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	18.37%	[2]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.93%	[2],[3]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Nov. 12, 2014	[2]
AB Global Core Equity Portfolio | Return After Taxes on Distributions and Sale of Fund Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	12.01%	[2]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	5.73%	[2],[3]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Nov. 12, 2014	[2]
AB Global Core Equity Portfolio | MSCI ACWI Index (Net) (reflects no deduction for fees, expenses, or taxes except the reinvestment of dividends of non-U.S. withholding taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	23.97%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	8.69%	[3]

[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 contingent deferred sales charge, or 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] Inception date for all Classes: 11/12/14.

[4] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[5] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

XML

AB International Strategic Core Portfolio

AB INTERNATIONAL STRATEGIC CORE PORTFOLIO

INVESTMENT OBJECTIVE

The Fund’s investment objective is to seek long-term growth of capital.

FEES AND EXPENSES OF THE FUND

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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI").

You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB International Strategic Core Portfolio	CLASS A SHARES		CLASS C SHARES		ADVISOR CLASS SHARES
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.25%		none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	[1]	1.00%	[2]	none
Exchange Fee	none		none		none

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage<br/> of the value of your investment)

Annual Fund Operating Expenses - AB International Strategic Core Portfolio		CLASS A	CLASS C	ADVISOR CLASS
Management Fees		0.75%	0.75%	0.75%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	none
Other Expenses: Transfer Agent		0.04%	0.06%	0.04%
Other Expenses		0.89%	0.87%	0.86%
Total Other Expenses		0.93%	0.93%	0.90%
Acquired Fund Fees and Expenses		0.01%	0.01%	0.01%
Total Annual Fund Operating Expenses		1.94%	2.69%	1.66%
Fee Waiver and/or Expense Reimbursement	[1]	(0.74%)	(0.74%)	(0.71%)
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement		1.20%	1.95%	0.95%

EXAMPLE

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 these periods. The Examples also assume that your investment has a 5% return each year, that the Fund’s operating expenses stay the same and that any fee waiver remains in effect for only the first year. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - AB International Strategic Core Portfolio - USD ($)	CLASS A	CLASS C		ADVISOR CLASS
After 1 Year	$ 542	$ 298	[1]	$ 97
After 3 Years	940	765		454
After 5 Years	1,362	1,359		835
After 10 Years	$ 2,536	$ 2,968		$ 1,906

PORTFOLIO TURNOVER

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 period, the Fund's portfolio turnover rate was 53% of the average value of its portfolio.

PRINCIPAL STRATEGIES

The Adviser seeks to achieve the Fund’s investment objective by investing, under normal circumstances, primarily in common stocks of non-U.S. companies, and in companies in at least three countries other than the United States.

The Fund will invest in companies that are determined by the Adviser to offer favorable long-term sustainable profitability, price stability, and attractive valuations. The Adviser will employ an integrated approach that combines both fundamental and quantitative research to identify attractive investment opportunities. Factors that the Adviser will consider in this regard will include: a company’s record and projections of profitability, accuracy and availability of information with respect to the company, success and experience of management, competitive advantage, low stock price volatility, and liquidity of the company’s securities. The Adviser will compare these results to the characteristics of the general stock markets to determine the relative attractiveness of each company at a given time. The Adviser will weigh economic, political and market factors in making investment decisions. The Adviser will seek to manage the Fund so that it is subject to less share price volatility than many other international mutual funds, although there can be no guarantee that the Adviser will be successful in this regard.

The Fund will primarily invest in mid- and large-capitalization companies, which are currently defined for the Fund as companies that have market capitalizations of $1.5 billion or more. The Fund’s holdings of non-U.S. companies will generally include some companies located in emerging markets.

Fluctuations in currency exchange rates can have a dramatic impact on the returns of equity securities. The Adviser may adjust the foreign currency exposure resulting from the Fund’s security positions through the use of currency-related derivatives, primarily in an effort to minimize the currency risk to which the Fund is subject. However, the Adviser is not required to use such derivatives.

PRINCIPAL RISKS

• MARKET RISK: The value of the Fund’s assets will fluctuate as the stock or bond markets fluctuate. The value of the Fund’s investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market.

• SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund’s investments.

• 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. These risks may be heightened with respect to investments in emerging market countries, where there may be an increased amount of economic, political and social instability.

• CURRENCY RISK: Fluctuations in currency exchange rates may negatively affect the value of the Fund’s investments or reduce its returns.

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

• 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.

BAR CHART AND PERFORMANCE INFORMATION

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 the life of the Fund; and

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

You may obtain updated performance information on the Fund’s website at www.abfunds.com (click on “Investments--Mutual Funds”).

The Fund’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.

BAR CHART

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, 2018, the year-to-date unannualized return for Class A shares was 3.39%.

During the period shown in the bar chart, the Fund’s:

BEST QUARTER WAS UP 7.92%, 2ND QUARTER, 2017; AND WORST QUARTER WAS DOWN
-4.72%, 4TH QUARTER, 2016.

PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the period ended December 31, 2017)

Average Annual Total Returns - AB International Strategic Core Portfolio		1 YEAR	SINCE INCEPTION	[2]	INCEPTION DATE
CLASS A	[1]	18.94%	6.58%		Jul. 29, 2015
CLASS A | Return After Taxes on Distributions	[1]	18.70%	6.23%		Jul. 29, 2015
CLASS A | Return After Taxes on Distributions and Sale of Fund Shares	[1]	11.03%	5.02%		Jul. 29, 2015
CLASS C		22.28%	7.67%		Jul. 29, 2015
ADVISOR CLASS		24.61%	8.73%		Jul. 29, 2015
MSCI EAFE Index (reflects no deduction for fees, expenses or taxes)		25.03%	6.84%

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[1] The Adviser has contractually agreed to waive its management fees and/or to bear expenses of the Fund until October 31, 2019 to the extent necessary to prevent total Fund operating expenses (excluding acquired fund fees and expenses other than the advisory fees of any AB Mutual Funds in which the Fund may invest, interest expense and extraordinary expenses), on an annualized basis, from exceeding 1.20%, 1.95% and .95% of average daily net assets, respectively, for Class A, Class C and Advisor Class shares ("expense limitations"). The expense limitations will remain in effect until October 31, 2019 and will continue thereafter from year to year unless the Adviser provides notice of termination to the Fund at least 60 days prior to the end of the period. Any fees waived and expenses borne by the Adviser may be reimbursed by the Fund until the end of the third fiscal year after the fiscal period in which the fee was waived or the expense was borne, provided that no reimbursement payment will be made that would cause the Fund's covered operating expenses to exceed the applicable expense limitations. In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[1] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

[1] 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.

[2] Inception date for all Classes: 7/29/15.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
AB International Strategic Core Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB INTERNATIONAL STRATEGIC CORE PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund’s investment objective is to seek 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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs for Class A Shares on page 130 of the Fund's Statement of Additional Information ("SAI"). You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.
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<br/> of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	October 31, 2019
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 period, the Fund's portfolio turnover rate was 53% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	53.00%
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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances. For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.
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 AB Mutual Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 100,000
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE
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 these periods. The Examples also assume that your investment has a 5% return each year, that the Fund’s operating expenses stay the same and that any fee waiver remains 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]	rr_StrategyHeading	PRINCIPAL STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Adviser seeks to achieve the Fund’s investment objective by investing, under normal circumstances, primarily in common stocks of non-U.S. companies, and in companies in at least three countries other than the United States. The Fund will invest in companies that are determined by the Adviser to offer favorable long-term sustainable profitability, price stability, and attractive valuations. The Adviser will employ an integrated approach that combines both fundamental and quantitative research to identify attractive investment opportunities. Factors that the Adviser will consider in this regard will include: a company’s record and projections of profitability, accuracy and availability of information with respect to the company, success and experience of management, competitive advantage, low stock price volatility, and liquidity of the company’s securities. The Adviser will compare these results to the characteristics of the general stock markets to determine the relative attractiveness of each company at a given time. The Adviser will weigh economic, political and market factors in making investment decisions. The Adviser will seek to manage the Fund so that it is subject to less share price volatility than many other international mutual funds, although there can be no guarantee that the Adviser will be successful in this regard. The Fund will primarily invest in mid- and large-capitalization companies, which are currently defined for the Fund as companies that have market capitalizations of $1.5 billion or more. The Fund’s holdings of non-U.S. companies will generally include some companies located in emerging markets. Fluctuations in currency exchange rates can have a dramatic impact on the returns of equity securities. The Adviser may adjust the foreign currency exposure resulting from the Fund’s security positions through the use of currency-related derivatives, primarily in an effort to minimize the currency risk to which the Fund is subject. However, the Adviser is not required to use such derivatives.
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 markets fluctuate. The value of the Fund’s investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund’s investments. 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. These risks may be heightened with respect to investments in emerging market countries, where there may be an increased amount of economic, political and social instability. CURRENCY RISK: Fluctuations in currency exchange rates may negatively affect the value of the Fund’s investments or reduce its returns. CAPITALIZATION RISK: Investments in mid-capitalization companies may be more volatile than investments in large-capitalization companies. Investments in mid-capitalization companies may have additional risks because these companies have limited product lines, markets or financial resources. 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 the life of the Fund; and how the Fund’s average annual returns for one year and since inception compare to those of a broad-based securities market index. You may obtain updated performance information on the Fund’s website at www.abfunds.com (click on “Investments--Mutual Funds”). 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	<ul type="square"><li>how the Fund’s performance changed from year to year over the life of the Fund; and </li></ul><ul type="square"><li> how the Fund’s average annual returns for one year and since inception compare to those of a broad-based securities market index.</li></ul>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.abfunds.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, 2018, the year-to-date unannualized return for Class A shares was 3.39%.
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 7.92%, 2ND QUARTER, 2017; AND WORST QUARTER WAS DOWN -4.72%, 4TH QUARTER, 2016.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the period ended December 31, 2017)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax Returns: -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	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.
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;
AB International Strategic Core Portfolio | CLASS A
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.89%
Total Other Expenses	rr_OtherExpensesOverAssets	0.93%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.94%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.74%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.20%
After 1 Year	rr_ExpenseExampleYear01	$ 542
After 3 Years	rr_ExpenseExampleYear03	940
After 5 Years	rr_ExpenseExampleYear05	1,362
After 10 Years	rr_ExpenseExampleYear10	$ 2,536
2008	rr_AnnualReturn2008
2009	rr_AnnualReturn2009
2010	rr_AnnualReturn2010
2011	rr_AnnualReturn2011
2012	rr_AnnualReturn2012
2013	rr_AnnualReturn2013
2014	rr_AnnualReturn2014
2015	rr_AnnualReturn2015
2016	rr_AnnualReturn2016	(0.30%)
2017	rr_AnnualReturn2017	24.26%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	3.39%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2017
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	7.92%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2016
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.72%)
1 YEAR	rr_AverageAnnualReturnYear01	18.94%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.58%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jul. 29, 2015	[3]
AB International Strategic Core Portfolio | CLASS C
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%	[5]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.06%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.87%
Total Other Expenses	rr_OtherExpensesOverAssets	0.93%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.69%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.74%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.95%
After 1 Year	rr_ExpenseExampleYear01	$ 298	[6]
After 3 Years	rr_ExpenseExampleYear03	765
After 5 Years	rr_ExpenseExampleYear05	1,359
After 10 Years	rr_ExpenseExampleYear10	$ 2,968
1 YEAR	rr_AverageAnnualReturnYear01	22.28%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	7.67%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jul. 29, 2015
AB International Strategic Core Portfolio | ADVISOR CLASS
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.75%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.86%
Total Other Expenses	rr_OtherExpensesOverAssets	0.90%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.66%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.71%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.95%
After 1 Year	rr_ExpenseExampleYear01	$ 97
After 3 Years	rr_ExpenseExampleYear03	454
After 5 Years	rr_ExpenseExampleYear05	835
After 10 Years	rr_ExpenseExampleYear10	$ 1,906
1 YEAR	rr_AverageAnnualReturnYear01	24.61%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	8.73%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jul. 29, 2015
AB International Strategic Core Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	18.70%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.23%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jul. 29, 2015	[3]
AB International Strategic Core Portfolio | Return After Taxes on Distributions and Sale of Fund Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	11.03%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	5.02%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jul. 29, 2015	[3]
AB International Strategic Core Portfolio | MSCI EAFE Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	25.03%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.84%	[4]

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] The Adviser has contractually agreed to waive its management fees and/or to bear expenses of the Fund until October 31, 2019 to the extent necessary to prevent total Fund operating expenses (excluding acquired fund fees and expenses other than the advisory fees of any AB Mutual Funds in which the Fund may invest, interest expense and extraordinary expenses), on an annualized basis, from exceeding 1.20%, 1.95% and .95% of average daily net assets, respectively, for Class A, Class C and Advisor Class shares ("expense limitations"). The expense limitations will remain in effect until October 31, 2019 and will continue thereafter from year to year unless the Adviser provides notice of termination to the Fund at least 60 days prior to the end of the period. Any fees waived and expenses borne by the Adviser may be reimbursed by the Fund until the end of the third fiscal year after the fiscal period in which the fee was waived or the expense was borne, provided that no reimbursement payment will be made that would cause the Fund's covered operating expenses to exceed the applicable expense limitations. In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[3] 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.

[4] Inception date for all Classes: 7/29/15.

[5] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[6] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

XML

AB Concentrated International Growth Portfolio

AB CONCENTRATED INTERNATIONAL GROWTH PORTFOLIO

INVESTMENT OBJECTIVE

The Fund’s investment objective is to seek long-term growth of capital.

FEES AND EXPENSES OF THE FUND

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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs on page 130 of the Fund’s Statement of Additional Information (“SAI”).

You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB Concentrated International Growth Portfolio	CLASS A SHARES		CLASS C SHARES		ADVISOR CLASS SHARES
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.25%		none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	[1]	1.00%	[2]	none
Exchange Fee	none		none		none

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage<br/>of the value of your investment)

Annual Fund Operating Expenses - AB Concentrated International Growth Portfolio		CLASS A	CLASS C	ADVISOR CLASS
Management Fees		0.85%	0.85%	0.85%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	none
Other Expenses: Transfer Agent		0.05%	0.08%	0.05%
Other Expenses		0.93%	0.96%	0.90%
Total Other Expenses		0.98%	1.04%	0.95%
Acquired Fund Fees and Expenses		0.01%	0.01%	0.01%
Total Annual Fund Operating Expenses		2.09%	2.90%	1.81%
Fee Waiver and/or Expense Reimbursement	[1]	(0.79%)	(0.85%)	(0.76%)
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement		1.30%	2.05%	1.05%

EXAMPLE

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 these periods. The Examples also assume that your investment has a 5% return each year, that the Fund’s operating expenses stay the same and that any fee waiver remains in effect for only the first year. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example - AB Concentrated International Growth Portfolio - USD ($)	CLASS A	CLASS C		ADVISOR CLASS
After 1 Year	$ 552	$ 308	[1]	$ 107
After 3 Years	979	818		495
After 5 Years	1,431	1,453		909
After 10 Years	$ 2,683	$ 3,163		$ 2,064

PORTFOLIO TURNOVER

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 34% of the average value of its portfolio.

PRINCIPAL STRATEGIES

The Adviser seeks to achieve the Fund’s investment objective by investing, under normal circumstances, primarily in common stocks of non-U.S. companies, and in companies in at least three countries other than the United States.

The Fund will invest in companies that are determined by the Adviser to offer favorable long-term growth potential and that are trading at attractive valuations. The Adviser will employ an appraisal method which attempts to measure each prospective company’s quality and growth rate by numerous factors. Such factors will include: a company’s record and projections of profit and earnings growth, accuracy and availability of information with respect to the company, success and experience of management, accessibility of management to the Adviser, product lines and competitive position both in the United States and abroad, lack of cyclicality, large market capitalization and liquidity of the company’s securities. The Adviser will compare these results to the characteristics of the general stock markets to determine the relative attractiveness of each company at a given time. The Adviser will weigh economic, political and market factors in making investment decisions; this appraisal technique attempts to measure each investment candidate not only against other stocks of the same industry and region, but also against a broad spectrum of investments.

The Fund will invest in a relatively small number of individual stocks, generally 25 to 35 companies. The Fund will primarily invest in mid- and large-capitalization companies, which are currently defined for the Fund as companies that have market capitalizations of $2.0 billion or more. The Fund’s holdings of non-U.S. companies may include some companies located in emerging markets, and at times emerging market companies may make up a significant portion of the Fund.

Fluctuations in currency exchange rates can have a dramatic impact of the returns of equity securities. While the Adviser may hedge the foreign currency exposure resulting from the Fund’s security positions through the use of currency-related derivatives, it is not required to do so.

PRINCIPAL RISKS

• 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 the Fund’s growth approach, may underperform the market generally.

• SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund’s investments.

• 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.

• 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 Fund’s investments or reduce its returns.

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

• 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.

BAR CHART AND PERFORMANCE INFORMATION

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 the life of the Fund; and

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

You may obtain updated performance information on the Fund’s website at www.abfunds.com (click on “Investments--Mutual Funds”).

The Fund’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.

BAR CHART

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, 2018, the year-to-date unannualized return for Class A shares was -1.13%.

During the period shown in the bar chart, the Fund's:

BEST QUARTER WAS UP 10.69%, 1ST QUARTER, 2017; AND WORST QUARTER WAS DOWN
-6.07%, 4TH QUARTER, 2016.

PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the period ended December 31, 2017)

Average Annual Total Returns - AB Concentrated International Growth Portfolio		1 YEAR	SINCE INCEPTION	[2]	INCEPTION DATE
CLASS A	[1]	31.68%	4.97%		Apr. 15, 2015
CLASS A | Return After Taxes on Distributions	[1]	30.33%	4.56%		Apr. 15, 2015
CLASS A | Return After Taxes on Distributions and Sale of Fund Shares	[1]	18.33%	3.74%		Apr. 15, 2015
CLASS C		35.55%	5.88%		Apr. 15, 2015
ADVISOR CLASS		37.85%	6.93%		Apr. 15, 2015
MSCI EAFE Index (reflects no deduction for fees, expenses or taxes)		25.03%	5.58%

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[1] The Adviser has contractually agreed to waive its management fees and/or to bear expenses of the Fund until October 31, 2019 to the extent necessary to prevent total Fund operating expenses (excluding acquired fund fees and expenses other than the advisory fees of any AB Mutual Funds in which the Fund may invest, interest expense and extraordinary expenses), on an annualized basis, from exceeding 1.30%, 2.05% and 1.05% of average daily net assets, respectively, for Class A, Class C and Advisor Class shares ("expense limitations"). The expense limitations will remain in effect until October 31, 2019 and will continue thereafter from year to year unless the Adviser provides notice of termination to the Fund at least 60 days prior to the end of the period. Any fees waived and expenses borne by the Adviser may be reimbursed by the Fund until the end of the third fiscal year after the fiscal period in which the fee was waived or the expense was borne, provided that no reimbursement payment will be made that would cause the Fund's covered operating expenses to exceed the applicable expense limitations. In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[1] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

[1] 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.

[2] Inception date for all Classes: 4/15/15.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
AB Concentrated International Growth Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB CONCENTRATED INTERNATIONAL GROWTH PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund’s investment objective is to seek 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 AB 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 66 of this Prospectus, in Appendix B--Financial Intermediary Waivers of this Prospectus and in Purchase of Shares--Sales Charge Reduction Programs on page 130 of the Fund’s Statement of Additional Information (“SAI”). You may be required to pay commissions and/or other forms of compensation to a broker for transactions in Advisor Class shares, which are not reflected in the tables or the examples below.
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<br/>of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	October 31, 2019
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 34% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	34.00%
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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances. For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.
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 AB Mutual Funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 100,000
Expense Example [Heading]	rr_ExpenseExampleHeading	EXAMPLE
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 these periods. The Examples also assume that your investment has a 5% return each year, that the Fund’s operating expenses stay the same and that any fee waiver remains 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]	rr_StrategyHeading	PRINCIPAL STRATEGIES
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Adviser seeks to achieve the Fund’s investment objective by investing, under normal circumstances, primarily in common stocks of non-U.S. companies, and in companies in at least three countries other than the United States. The Fund will invest in companies that are determined by the Adviser to offer favorable long-term growth potential and that are trading at attractive valuations. The Adviser will employ an appraisal method which attempts to measure each prospective company’s quality and growth rate by numerous factors. Such factors will include: a company’s record and projections of profit and earnings growth, accuracy and availability of information with respect to the company, success and experience of management, accessibility of management to the Adviser, product lines and competitive position both in the United States and abroad, lack of cyclicality, large market capitalization and liquidity of the company’s securities. The Adviser will compare these results to the characteristics of the general stock markets to determine the relative attractiveness of each company at a given time. The Adviser will weigh economic, political and market factors in making investment decisions; this appraisal technique attempts to measure each investment candidate not only against other stocks of the same industry and region, but also against a broad spectrum of investments. The Fund will invest in a relatively small number of individual stocks, generally 25 to 35 companies. The Fund will primarily invest in mid- and large-capitalization companies, which are currently defined for the Fund as companies that have market capitalizations of $2.0 billion or more. The Fund’s holdings of non-U.S. companies may include some companies located in emerging markets, and at times emerging market companies may make up a significant portion of the Fund. Fluctuations in currency exchange rates can have a dramatic impact of the returns of equity securities. While the Adviser may hedge the foreign currency exposure resulting from the Fund’s security positions through the use of currency-related derivatives, it is not required to do so.
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 the Fund’s growth approach, may underperform the market generally. SECTOR RISK: The Fund may have more risk because of concentrated investments in a particular market sector, such as the technology or financial services sector. Market or economic factors affecting that sector could have a major effect on the value of the Fund’s investments. 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. 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 Fund’s investments or reduce its returns. CAPITALIZATION RISK: Investments in mid-capitalization companies may be more volatile than investments in large-capitalization companies. Investments in mid-capitalization companies may have additional risks because these companies have limited product lines, markets or financial resources. 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 the life of the Fund; and how the Fund’s average annual returns for one year and since inception compare to those of a broad-based securities market index. You may obtain updated performance information on the Fund’s website at www.abfunds.com (click on “Investments--Mutual Funds”). 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	<ul type="square"><li> how the Fund’s performance changed from year to year over the life of the Fund; and</li></ul><ul type="square"><li> how the Fund’s average annual returns for one year and since inception compare to those of a broad-based securities market index. </li></ul>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.abfunds.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, 2018, the year-to-date unannualized return for Class A shares was -1.13%.
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 10.69%, 1ST QUARTER, 2017; AND WORST QUARTER WAS DOWN -6.07%, 4TH QUARTER, 2016.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<br/><br/>(For the period ended December 31, 2017)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax Returns: -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	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.
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;
AB Concentrated International Growth Portfolio | CLASS A
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.93%
Total Other Expenses	rr_OtherExpensesOverAssets	0.98%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.09%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.79%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.30%
After 1 Year	rr_ExpenseExampleYear01	$ 552
After 3 Years	rr_ExpenseExampleYear03	979
After 5 Years	rr_ExpenseExampleYear05	1,431
After 10 Years	rr_ExpenseExampleYear10	$ 2,683
2008	rr_AnnualReturn2008
2009	rr_AnnualReturn2009
2010	rr_AnnualReturn2010
2011	rr_AnnualReturn2011
2012	rr_AnnualReturn2012
2013	rr_AnnualReturn2013
2014	rr_AnnualReturn2014
2015	rr_AnnualReturn2015
2016	rr_AnnualReturn2016	(5.97%)
2017	rr_AnnualReturn2017	37.49%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(1.13%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2017
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	10.69%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2016
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(6.07%)
1 YEAR	rr_AverageAnnualReturnYear01	31.68%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	4.97%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Apr. 15, 2015	[3]
AB Concentrated International Growth Portfolio | CLASS C
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%	[5]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.08%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.96%
Total Other Expenses	rr_OtherExpensesOverAssets	1.04%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.90%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.85%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	2.05%
After 1 Year	rr_ExpenseExampleYear01	$ 308	[6]
After 3 Years	rr_ExpenseExampleYear03	818
After 5 Years	rr_ExpenseExampleYear05	1,453
After 10 Years	rr_ExpenseExampleYear10	$ 3,163
1 YEAR	rr_AverageAnnualReturnYear01	35.55%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	5.88%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Apr. 15, 2015
AB Concentrated International Growth Portfolio | ADVISOR CLASS
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_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.85%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component2OtherExpensesOverAssets	0.90%
Total Other Expenses	rr_OtherExpensesOverAssets	0.95%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.81%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.76%)	[2]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.05%
After 1 Year	rr_ExpenseExampleYear01	$ 107
After 3 Years	rr_ExpenseExampleYear03	495
After 5 Years	rr_ExpenseExampleYear05	909
After 10 Years	rr_ExpenseExampleYear10	$ 2,064
1 YEAR	rr_AverageAnnualReturnYear01	37.85%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.93%	[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Apr. 15, 2015
AB Concentrated International Growth Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	30.33%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	4.56%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Apr. 15, 2015	[3]
AB Concentrated International Growth Portfolio | Return After Taxes on Distributions and Sale of Fund Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	18.33%	[3]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	3.74%	[3],[4]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Apr. 15, 2015	[3]
AB Concentrated International Growth Portfolio | MSCI EAFE Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	25.03%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	5.58%	[4]

[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 contingent deferred sales charge, or CDSC, which may be subject to waiver in certain circumstances.

[2] The Adviser has contractually agreed to waive its management fees and/or to bear expenses of the Fund until October 31, 2019 to the extent necessary to prevent total Fund operating expenses (excluding acquired fund fees and expenses other than the advisory fees of any AB Mutual Funds in which the Fund may invest, interest expense and extraordinary expenses), on an annualized basis, from exceeding 1.30%, 2.05% and 1.05% of average daily net assets, respectively, for Class A, Class C and Advisor Class shares ("expense limitations"). The expense limitations will remain in effect until October 31, 2019 and will continue thereafter from year to year unless the Adviser provides notice of termination to the Fund at least 60 days prior to the end of the period. Any fees waived and expenses borne by the Adviser may be reimbursed by the Fund until the end of the third fiscal year after the fiscal period in which the fee was waived or the expense was borne, provided that no reimbursement payment will be made that would cause the Fund's covered operating expenses to exceed the applicable expense limitations. In connection with the Fund's investments in AB Government Money Market Portfolio (the "Money Market Portfolio"), the Adviser has contractually agreed to waive its management fee from the Fund and/or reimburse other expenses of the Fund in an amount equal to the Fund's pro rata share of the Money Market Portfolio's effective management fee, as included in "Acquired Fund Fees and Expenses".

[3] 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.

[4] Inception date for all Classes: 4/15/15.

[5] For Class C shares, the CDSC is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[6] If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB CAP FUND, INC.
Prospectus Date	rr_ProspectusDate	Oct. 31, 2018
Document Creation Date	dei_DocumentCreationDate	Oct. 26, 2018