497

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	497
Document Period End Date	dei_DocumentPeriodEndDate	May 31, 2018
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Central Index Key	dei_EntityCentralIndexKey	0000798737
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Sep. 28, 2018
Document Effective Date	dei_DocumentEffectiveDate	Sep. 28, 2018
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018

XML

AB MUNICIPAL INCOME FUND, INC. | AB National Portfolio

SUMMARY INFORMATION <br/><br/>AB NATIONAL PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income, exempt from federal income tax, that is available without assuming what the Adviser considers to be undue risk to principal or income.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 MUNICIPAL INCOME FUND, INC. - AB National Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES		ADVISOR CLASS SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]	none
Exchange Fee	none	none		none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND, INC. - AB National Portfolio		CLASS A	CLASS B	CLASS C	ADVISOR CLASS
Management Fees		0.45%	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none
Other Expenses: Transfer Agent		0.04%	0.05%	0.04%	0.04%
Other Expenses		0.06%	0.06%	0.06%	0.06%
Total Other Expenses		0.10%	0.11%	0.10%	0.10%
Total Annual Portfolio Operating Expenses	[1]	0.80%	1.56%	1.55%	0.55%
Fee Waiver and/or Expense Reimbursement	[2]	(0.05%)	(0.06%)	(0.05%)	(0.05%)
Total Annual Portfolio Operating Expenses	[3]	0.75%	1.50%	1.50%	0.50%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year and that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND, INC. - AB National Portfolio - USD ($)	CLASS A	CLASS B	CLASS C	ADVISOR CLASS
After 1 Year	$ 374	$ 453	$ 253	$ 51
After 3 Years	543	587	485	171
After 5 Years	726	844	840	302
After 10 Years	$ 1,256	$ 1,459	$ 1,841	$ 684

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 MUNICIPAL INCOME FUND, INC. - AB National Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 153	$ 153
After 3 Years	487	485
After 5 Years	844	840
After 10 Years	$ 1,459	$ 1,841

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 18% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. The Portfolio may invest more than 25% of its assets in a single state.

The Portfolio may also invest in:

• forward commitments;

• tender option bonds ("TOBs");

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. To the extent that the Portfolio invests more of its assets in a particular state's municipal securities, the Portfolio may be vulnerable to events adversely affecting that state, including economic, political and regulatory occurrences, court decisions, terrorism and catastrophic natural disasters, such as hurricanes or earthquakes. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.42%.

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

BEST QUARTER WAS UP 7.66%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.69%, 4TH QUARTER, 2008.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND, INC. - AB National Portfolio		1 YEAR	5 YEARS	10 YEARS	INCEPTION DATE
CLASS A	[1]	2.58%	2.19%	3.91%
CLASS A | Return After Taxes on Distributions	[1]	2.57%	2.18%	3.89%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	2.77%	2.41%	3.86%
CLASS B		1.95%	2.07%	3.80%
CLASS C		3.95%	2.08%	3.49%
ADVISOR CLASS	[2]	6.00%	3.10%	4.52%	Aug. 06, 2008
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[2] Inception date for Advisor Class shares: 8/6/2008. Performance information for periods prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND, INC. | AB National Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	SUMMARY INFORMATION <br/><br/>AB NATIONAL PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income, exempt from federal income tax, that is available without assuming what the Adviser considers to be undue risk to principal or income.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 18% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	18.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year and that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. The Portfolio may invest more than 25% of its assets in a single state. The Portfolio may also invest in: forward commitments; tender option bonds ("TOBs"); zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. To the extent that the Portfolio invests more of its assets in a particular state's municipal securities, the Portfolio may be vulnerable to events adversely affecting that state, including economic, political and regulatory occurrences, court decisions, terrorism and catastrophic natural disasters, such as hurricanes or earthquakes. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li>how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.42%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 7.66%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.69%, 4TH QUARTER, 2008.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND, INC. | AB National Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.10%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.80%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.75%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 374
After 3 Years	rr_ExpenseExampleYear03	543
After 5 Years	rr_ExpenseExampleYear05	726
After 10 Years	rr_ExpenseExampleYear10	$ 1,256
2008	rr_AnnualReturn2008	(9.41%)
2009	rr_AnnualReturn2009	16.86%
2010	rr_AnnualReturn2010	3.54%
2011	rr_AnnualReturn2011	10.71%
2012	rr_AnnualReturn2012	8.48%
2013	rr_AnnualReturn2013	(4.39%)
2014	rr_AnnualReturn2014	10.03%
2015	rr_AnnualReturn2015	2.94%
2016	rr_AnnualReturn2016	0.34%
2017	rr_AnnualReturn2017	5.74%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.42%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	7.66%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.69%)
1 YEAR	rr_AverageAnnualReturnYear01	2.58%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	2.19%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.91%	[4]
AB MUNICIPAL INCOME FUND, INC. | AB National 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	3.00%	[5]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.11%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.56%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.50%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 453
After 3 Years	rr_ExpenseExampleYear03	587
After 5 Years	rr_ExpenseExampleYear05	844
After 10 Years	rr_ExpenseExampleYear10	1,459
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	153
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	487
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	844
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,459
1 YEAR	rr_AverageAnnualReturnYear01	1.95%
5 YEARS	rr_AverageAnnualReturnYear05	2.07%
10 YEARS	rr_AverageAnnualReturnYear10	3.80%
AB MUNICIPAL INCOME FUND, INC. | AB National 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%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.10%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.55%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.50%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 253
After 3 Years	rr_ExpenseExampleYear03	485
After 5 Years	rr_ExpenseExampleYear05	840
After 10 Years	rr_ExpenseExampleYear10	1,841
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	153
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	485
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	840
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,841
1 YEAR	rr_AverageAnnualReturnYear01	3.95%
5 YEARS	rr_AverageAnnualReturnYear05	2.08%
10 YEARS	rr_AverageAnnualReturnYear10	3.49%
AB MUNICIPAL INCOME FUND, INC. | AB National 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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.10%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.55%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.05%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.50%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 51
After 3 Years	rr_ExpenseExampleYear03	171
After 5 Years	rr_ExpenseExampleYear05	302
After 10 Years	rr_ExpenseExampleYear10	$ 684
1 YEAR	rr_AverageAnnualReturnYear01	6.00%	[7]
5 YEARS	rr_AverageAnnualReturnYear05	3.10%	[7]
10 YEARS	rr_AverageAnnualReturnYear10	4.52%	[7]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Aug. 06, 2008	[7]
AB MUNICIPAL INCOME FUND, INC. | AB National Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.57%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	2.18%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.89%	[4]
AB MUNICIPAL INCOME FUND, INC. | AB National Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.77%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	2.41%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.86%	[4]
AB MUNICIPAL INCOME FUND, INC. | AB National Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[5] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

[7] Inception date for Advisor Class shares: 8/6/2008. Performance information for periods prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

XML

AB MUNICIPAL INCOME FUND, INC. | AB High Income Municipal Portfolio

AB HIGH INCOME MUNICIPAL PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income, exempt from federal income tax, that is available consistent with what the Adviser considers to be an appropriate level of risk.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 MUNICIPAL INCOME FUND, INC. - AB High Income Municipal Portfolio	CLASS A SHARES	CLASS C SHARES		ADVISOR CLASS SHARES	CLASS Z SHARES
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none	none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	1.00%	[1]	none	none
Exchange Fee	none	none		none	none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND, INC. - AB High Income Municipal Portfolio		CLASS A	CLASS C	ADVISOR CLASS	CLASS Z
Management Fees		0.50%	0.50%	0.50%	0.50%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	none	none
Other Expenses: Transfer Agent		0.03%	0.03%	0.03%	0.02%
Other Expenses: Interest Expense		0.07%	0.07%	0.07%	0.07%
Other Expenses		0.03%	0.03%	0.03%	0.03%
Total Other Expenses		0.13%	0.13%	0.13%	0.12%	[1]
Total Annual Portfolio Operating Expenses	[2]	0.88%	1.63%	0.63%	0.62%
Fee Waiver and/or Expense Reimbursement	[3]	(0.01%)	(0.01%)	(0.01%)	none
Total Annual Portfolio Operating Expenses	[4],[5]	0.87%	1.62%	0.62%	0.62%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of these periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND, INC. - AB High Income Municipal Portfolio - USD ($)	CLASS A	CLASS C		ADVISOR CLASS	CLASS Z
After 1 Year	$ 386	$ 265	[1]	$ 63	$ 63
After 3 Years	571	513		201	199
After 5 Years	772	886		350	346
After 10 Years	$ 1,351	$ 1,932		$ 785	$ 774

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 22% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding municipal securities that may be non-investment grade or investment grade. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers.

The Adviser selects securities for purchase or sale based on its assessment of the securities' risk and return characteristics as well as the securities' impact on the overall risk and return characteristics of the Portfolio. In making this assessment, the Adviser takes into account various factors including the credit quality and sensitivity to interest rates of the securities under consideration and of the Portfolio's other holdings.

The Portfolio may invest without limit in lower-rated securities ("junk bonds"), which may include securities having the lowest rating, and in unrated securities that, in the Adviser's judgment, would be lower-rated securities if rated. The Portfolio may invest in fixed-income securities with any maturity or duration. The Portfolio will seek to increase income for shareholders by investing in longer-maturity bonds. Consistent with its objective of seeking a higher level of income, the Portfolio may experience greater volatility and a higher risk of loss of principal than other municipal funds.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities;

• certain types of mortgage-related securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

The Portfolio may make short sales of securities or maintain a short position, and may use other investment techniques. The Portfolio may use leverage for investment purposes to increase income through the use of tender option bonds ("TOBs") and derivative instruments, such as interest rate swaps.

PRINCIPAL RISKS:

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

• CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security.

• BELOW INVESTMENT GRADE SECURITIES RISK: Investments in fixed-income securities with lower ratings (commonly known as "junk bonds") have a higher probability that an issuer will default or fail to meet its payment obligations. These securities may be subject to greater price volatility due to such factors as specific corporate developments, interest rate sensitivity, negative performance of the junk bond market generally and less secondary market liquidity.

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. To the extent that the Portfolio invests more of its assets in a particular state's municipal securities, the Portfolio may be vulnerable to events adversely affecting that state, including economic, political and regulatory occurrences, court decisions, terrorism and catastrophic natural disasters, such as hurricanes or earthquakes. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LEVERAGE RISK: To the extent the Portfolio uses leveraging techniques, such as TOBs, its NAV may be more volatile because leverage tends to exaggerate the effect of changes in interest rates and any increase or decrease in the value of the Portfolio's investments.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed over the life of the Portfolio; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was 0.69%.

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

BEST QUARTER WAS UP 6.45%, 1ST QUARTER, 2014; AND WORST QUARTER WAS DOWN -6.66%, 4TH QUARTER, 2016.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND, INC. - AB High Income Municipal Portfolio		1 YEAR	5 YEARS	SINCE INCEPTION	[2]	INCEPTION DATE
CLASS A	[1]	6.59%	3.87%	6.40%		Jan. 26, 2010
CLASS A | Return After Taxes on Distributions	[1]	6.57%	3.81%	6.30%		Jan. 26, 2010
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	5.50%	3.91%	6.00%		Jan. 26, 2010
CLASS C		8.10%	3.76%	6.05%		Jan. 26, 2010
ADVISOR CLASS		10.19%	4.81%	7.11%		Jan. 26, 2010
CLASS Z		10.19%	4.77%	7.08%		Sep. 28, 2018
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.30%

[1] For Class C shares, the contingent deferred sales charge, or CDSC, is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

[1] Total Other Expenses are based on estimated amounts for the current fiscal year.

[2] Including Interest Expense Before Waiver

[3] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS C ADVISOR CLASS CLASS Z ----- 0.80% 1.55% 0.55% 0.55%

[5] Including Interest Expense After Fee Waiver and/or Expense Reimbursement

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[2] Inception date for Class A, Class C and Advisor Class shares: 1/26/2010. Inception date for Class Z shares: 9/28/2018. Performance information for periods prior to the inception of Class Z shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Class Z shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND, INC. | AB High Income Municipal Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB HIGH INCOME MUNICIPAL PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income, exempt from federal income tax, that is available consistent with what the Adviser considers to be an appropriate level of risk.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 22% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	22.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	For Class C shares, the contingent deferred sales charge, or 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of these periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 Portfolio pursues its objective by investing principally in high-yielding municipal securities that may be non-investment grade or investment grade. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. The Adviser selects securities for purchase or sale based on its assessment of the securities' risk and return characteristics as well as the securities' impact on the overall risk and return characteristics of the Portfolio. In making this assessment, the Adviser takes into account various factors including the credit quality and sensitivity to interest rates of the securities under consideration and of the Portfolio's other holdings. The Portfolio may invest without limit in lower-rated securities ("junk bonds"), which may include securities having the lowest rating, and in unrated securities that, in the Adviser's judgment, would be lower-rated securities if rated. The Portfolio may invest in fixed-income securities with any maturity or duration. The Portfolio will seek to increase income for shareholders by investing in longer-maturity bonds. Consistent with its objective of seeking a higher level of income, the Portfolio may experience greater volatility and a higher risk of loss of principal than other municipal funds. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; certain types of mortgage-related securities; and derivatives, such as options, futures contracts, forwards and swaps. The Portfolio may make short sales of securities or maintain a short position, and may use other investment techniques. The Portfolio may use leverage for investment purposes to increase income through the use of tender option bonds ("TOBs") and derivative instruments, such as interest rate swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. BELOW INVESTMENT GRADE SECURITIES RISK: Investments in fixed-income securities with lower ratings (commonly known as "junk bonds") have a higher probability that an issuer will default or fail to meet its payment obligations. These securities may be subject to greater price volatility due to such factors as specific corporate developments, interest rate sensitivity, negative performance of the junk bond market generally and less secondary market liquidity. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. To the extent that the Portfolio invests more of its assets in a particular state's municipal securities, the Portfolio may be vulnerable to events adversely affecting that state, including economic, political and regulatory occurrences, court decisions, terrorism and catastrophic natural disasters, such as hurricanes or earthquakes. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LEVERAGE RISK: To the extent the Portfolio uses leveraging techniques, such as TOBs, its NAV may be more volatile because leverage tends to exaggerate the effect of changes in interest rates and any increase or decrease in the value of the Portfolio's investments. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed over the life of the Portfolio; and how the Portfolio's average annual returns for one year, five years and since inception compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed over the life of the Portfolio; and</li></ul><ul type="square"><li> how the Portfolio's average annual returns for one year, five years and since inception compare to those of a broad-based securities market index.</li></ul>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.abfunds.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was 0.69%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 6.45%, 1ST QUARTER, 2014; AND WORST QUARTER WAS DOWN -6.66%, 4TH QUARTER, 2016.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND, INC. | AB High Income Municipal Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.07%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.03%
Total Other Expenses	rr_OtherExpensesOverAssets	0.13%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.88%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.87%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 386
After 3 Years	rr_ExpenseExampleYear03	571
After 5 Years	rr_ExpenseExampleYear05	772
After 10 Years	rr_ExpenseExampleYear10	$ 1,351
2008	rr_AnnualReturn2008
2009	rr_AnnualReturn2009
2010	rr_AnnualReturn2010
2011	rr_AnnualReturn2011	12.92%
2012	rr_AnnualReturn2012	16.61%
2013	rr_AnnualReturn2013	(7.95%)
2014	rr_AnnualReturn2014	17.20%
2015	rr_AnnualReturn2015	5.31%
2016	rr_AnnualReturn2016	(0.15%)
2017	rr_AnnualReturn2017	9.91%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	0.69%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2014
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.45%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2016
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(6.66%)
1 YEAR	rr_AverageAnnualReturnYear01	6.59%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	3.87%	[5]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.40%	[5],[6]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jan. 26, 2010	[5]
AB MUNICIPAL INCOME FUND, INC. | AB High Income Municipal 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%	[7]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.07%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.03%
Total Other Expenses	rr_OtherExpensesOverAssets	0.13%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.63%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.62%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 265	[8]
After 3 Years	rr_ExpenseExampleYear03	513
After 5 Years	rr_ExpenseExampleYear05	886
After 10 Years	rr_ExpenseExampleYear10	$ 1,932
1 YEAR	rr_AverageAnnualReturnYear01	8.10%
5 YEARS	rr_AverageAnnualReturnYear05	3.76%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.05%	[6]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jan. 26, 2010
AB MUNICIPAL INCOME FUND, INC. | AB High Income Municipal 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	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.07%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.03%
Total Other Expenses	rr_OtherExpensesOverAssets	0.13%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.63%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.01%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.62%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 63
After 3 Years	rr_ExpenseExampleYear03	201
After 5 Years	rr_ExpenseExampleYear05	350
After 10 Years	rr_ExpenseExampleYear10	$ 785
1 YEAR	rr_AverageAnnualReturnYear01	10.19%
5 YEARS	rr_AverageAnnualReturnYear05	4.81%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	7.11%	[6]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jan. 26, 2010
AB MUNICIPAL INCOME FUND, INC. | AB High Income Municipal 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	0.50%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.02%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.07%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.03%
Total Other Expenses	rr_OtherExpensesOverAssets	0.12%	[9]
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.62%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	none	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.62%	[3],[4]
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Total Other Expenses are based on estimated amounts for the current fiscal year.
After 1 Year	rr_ExpenseExampleYear01	$ 63
After 3 Years	rr_ExpenseExampleYear03	199
After 5 Years	rr_ExpenseExampleYear05	346
After 10 Years	rr_ExpenseExampleYear10	$ 774
1 YEAR	rr_AverageAnnualReturnYear01	10.19%
5 YEARS	rr_AverageAnnualReturnYear05	4.77%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	7.08%	[6]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND, INC. | AB High Income Municipal Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	6.57%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	3.81%	[5]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.30%	[5],[6]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jan. 26, 2010	[5]
AB MUNICIPAL INCOME FUND, INC. | AB High Income Municipal Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.50%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	3.91%	[5]
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	6.00%	[5],[6]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jan. 26, 2010	[5]
AB MUNICIPAL INCOME FUND, INC. | AB High Income Municipal Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
SINCE INCEPTION	rr_AverageAnnualReturnSinceInception	4.30%	[6]

[1] Including Interest Expense Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS C ADVISOR CLASS CLASS Z ----- 0.80% 1.55% 0.55% 0.55%

[4] Including Interest Expense After Fee Waiver and/or Expense Reimbursement

[5] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[6] Inception date for Class A, Class C and Advisor Class shares: 1/26/2010. Inception date for Class Z shares: 9/28/2018. Performance information for periods prior to the inception of Class Z shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Class Z shares.

[7] For Class C shares, the contingent deferred sales charge, or CDSC, is 0% after the first year. Class C shares automatically convert to Class A shares after ten years.

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

[9] Total Other Expenses are based on estimated amounts for the current fiscal year.

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AB MUNICIPAL INCOME FUND, INC. | AB California Portfolio

AB CALIFORNIA PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income, exempt from federal income tax and California personal income tax, that is available without assuming what the Adviser considers to be undue risk to income or principal.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 MUNICIPAL INCOME FUND, INC. - AB California Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES		ADVISOR CLASS SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]	none
Exchange Fee	none	none		none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND, INC. - AB California Portfolio		CLASS A	CLASS B	CLASS C	ADVISOR CLASS
Management Fees		0.45%	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none
Other Expenses: Transfer Agent		0.03%	0.07%	0.03%	0.03%
Other Expenses: Interest Expense		0.01%	0.01%	0.01%	0.01%
Other Expenses		0.06%	0.06%	0.06%	0.06%
Total Other Expenses		0.10%	0.14%	0.10%	0.10%
Total Annual Portfolio Operating Expenses	[1]	0.80%	1.59%	1.55%	0.55%
Fee Waiver and/or Expense Reimbursement	[2]	(0.04%)	(0.08%)	(0.04%)	(0.04%)
Total Annual Portfolio Operating Expenses	[3],[4]	0.76%	1.51%	1.51%	0.51%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND, INC. - AB California Portfolio - USD ($)	CLASS A	CLASS B	CLASS C	ADVISOR CLASS
After 1 Year	$ 375	$ 454	$ 254	$ 52
After 3 Years	544	594	486	172
After 5 Years	727	858	841	303
After 10 Years	$ 1,256	$ 1,475	$ 1,842	$ 685

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 MUNICIPAL INCOME FUND, INC. - AB California Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 154	$ 154
After 3 Years	494	486
After 5 Years	858	841
After 10 Years	$ 1,475	$ 1,842

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 14% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of California or municipal securities with interest that is otherwise exempt from California state income tax.

The Portfolio may also invest in:

• forward commitments;

• tender option bonds ("TOBs");

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in California municipal securities may be vulnerable to events adversely affecting its economy. California's economy, the largest of the 50 states, is relatively diverse, which makes it less vulnerable to events affecting a particular industry. Its economy, however, continues to be affected by fiscal constraints as a result of voter-passed initiatives that limit the ability of state and local governments to raise revenues, particularly with respect to real property taxes. California's economy may also be affected by natural disasters, such as earthquakes or fires. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.14%.

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

BEST QUARTER WAS UP 8.64%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.33%, 4TH QUARTER, 2010.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND, INC. - AB California Portfolio		1 YEAR	5 YEARS	10 YEARS	INCEPTION DATE
CLASS A	[1]	2.36%	2.39%	3.93%
CLASS A | Return After Taxes on Distributions	[1]	2.35%	2.37%	3.90%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	2.72%	2.58%	3.87%
CLASS B		1.73%	2.28%	3.81%
CLASS C		3.83%	2.28%	3.51%
ADVISOR CLASS	[2]	5.79%	3.29%	4.54%	Aug. 06, 2008
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Including Interest Expense Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ADVISOR CLASS ----- 0.75% 1.50% 1.50% 0.50%

[4] Including Interest Expense After Fee Waiver and/or Expense Reimbursement

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[2] Inception date for Advisor Class shares: 8/6/2008. Performance information for periods prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND, INC. | AB California Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB CALIFORNIA PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income, exempt from federal income tax and California personal income tax, that is available without assuming what the Adviser considers to be undue risk to income or principal.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 14% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	14.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of California or municipal securities with interest that is otherwise exempt from California state income tax. The Portfolio may also invest in: forward commitments; tender option bonds ("TOBs"); zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in California municipal securities may be vulnerable to events adversely affecting its economy. California's economy, the largest of the 50 states, is relatively diverse, which makes it less vulnerable to events affecting a particular industry. Its economy, however, continues to be affected by fiscal constraints as a result of voter-passed initiatives that limit the ability of state and local governments to raise revenues, particularly with respect to real property taxes. California's economy may also be affected by natural disasters, such as earthquakes or fires. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li> how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.14%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 8.64%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.33%, 4TH QUARTER, 2010.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br />AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND, INC. | AB California Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.10%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.80%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.04%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.76%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 375
After 3 Years	rr_ExpenseExampleYear03	544
After 5 Years	rr_ExpenseExampleYear05	727
After 10 Years	rr_ExpenseExampleYear10	$ 1,256
2008	rr_AnnualReturn2008	(7.31%)
2009	rr_AnnualReturn2009	14.03%
2010	rr_AnnualReturn2010	3.67%
2011	rr_AnnualReturn2011	10.74%
2012	rr_AnnualReturn2012	7.70%
2013	rr_AnnualReturn2013	(3.15%)
2014	rr_AnnualReturn2014	10.47%
2015	rr_AnnualReturn2015	3.17%
2016	rr_AnnualReturn2016	(0.42%)
2017	rr_AnnualReturn2017	5.53%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.14%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	8.64%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.33%)
1 YEAR	rr_AverageAnnualReturnYear01	2.36%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.39%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.93%	[5]
AB MUNICIPAL INCOME FUND, INC. | AB California 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	3.00%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.07%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.14%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.59%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.51%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 454
After 3 Years	rr_ExpenseExampleYear03	594
After 5 Years	rr_ExpenseExampleYear05	858
After 10 Years	rr_ExpenseExampleYear10	1,475
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	154
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	494
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	858
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,475
1 YEAR	rr_AverageAnnualReturnYear01	1.73%
5 YEARS	rr_AverageAnnualReturnYear05	2.28%
10 YEARS	rr_AverageAnnualReturnYear10	3.81%
AB MUNICIPAL INCOME FUND, INC. | AB California 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%	[7]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.10%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.55%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.04%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.51%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 254
After 3 Years	rr_ExpenseExampleYear03	486
After 5 Years	rr_ExpenseExampleYear05	841
After 10 Years	rr_ExpenseExampleYear10	1,842
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	154
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	486
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	841
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,842
1 YEAR	rr_AverageAnnualReturnYear01	3.83%
5 YEARS	rr_AverageAnnualReturnYear05	2.28%
10 YEARS	rr_AverageAnnualReturnYear10	3.51%
AB MUNICIPAL INCOME FUND, INC. | AB California 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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.06%
Total Other Expenses	rr_OtherExpensesOverAssets	0.10%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.55%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.04%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.51%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 52
After 3 Years	rr_ExpenseExampleYear03	172
After 5 Years	rr_ExpenseExampleYear05	303
After 10 Years	rr_ExpenseExampleYear10	$ 685
1 YEAR	rr_AverageAnnualReturnYear01	5.79%	[8]
5 YEARS	rr_AverageAnnualReturnYear05	3.29%	[8]
10 YEARS	rr_AverageAnnualReturnYear10	4.54%	[8]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Aug. 06, 2008	[8]
AB MUNICIPAL INCOME FUND, INC. | AB California Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.35%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.37%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.90%	[5]
AB MUNICIPAL INCOME FUND, INC. | AB California Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.72%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.58%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.87%	[5]
AB MUNICIPAL INCOME FUND, INC. | AB California Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Including Interest Expense Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ADVISOR CLASS ----- 0.75% 1.50% 1.50% 0.50%

[4] Including Interest Expense After Fee Waiver and/or Expense Reimbursement

[5] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[6] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

[8] Inception date for Advisor Class shares: 8/6/2008. Performance information for periods prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

XML

AB MUNICIPAL INCOME FUND II | AB Arizona Portfolio

AB ARIZONA PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and State of Arizona personal income tax that is available without assuming what the Adviser considers to be undue risk.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB MUNICIPAL INCOME FUND II - AB Arizona Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]
Exchange Fee	none	none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND II - AB Arizona Portfolio		CLASS A	CLASS B		CLASS C
Management Fees		0.45%	0.45%		0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%		1.00%
Other Expenses: Transfer Agent		0.04%	0.05%		0.04%
Other Expenses: Interest Expense		0.01%	none		0.01%
Other Expenses		0.25%	0.24%		0.25%
Total Other Expenses		0.30%	0.29%		0.30%
Total Annual Portfolio Operating Expenses	[1]	1.00%	1.74%		1.75%
Fee Waiver and/or Expense Reimbursement	[2]	(0.21%)	(0.21%)		(0.21%)
Total Annual Portfolio Operating Expenses	[3],[4]	0.79%	1.53%	[5]	1.54%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND II - AB Arizona Portfolio - USD ($)	CLASS A	CLASS B	CLASS C
After 1 Year	$ 378	$ 456	$ 257
After 3 Years	589	628	531
After 5 Years	816	924	929
After 10 Years	$ 1,469	$ 1,658	$ 2,045

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 MUNICIPAL INCOME FUND II - AB Arizona Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 156	$ 157
After 3 Years	528	531
After 5 Years	924	929
After 10 Years	$ 1,658	$ 2,045

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 12% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Arizona or municipal securities with interest that is otherwise exempt from Arizona state income tax.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Arizona municipal securities are vulnerable to events adversely affecting its economy. The leading sectors of Arizona's economy are the real estate and rental industries, tourism and wholesale trade. Construction is also an important sector due to the rapid growth of Arizona's population in recent years. These sectors are particularly vulnerable to times of impaired consumer and business spending. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.08%.

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

BEST QUARTER WAS UP 5.95%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -3.70%, 4TH QUARTER, 2010.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND II - AB Arizona Portfolio		1 YEAR	5 YEARS	10 YEARS
CLASS A	[1]	1.85%	2.28%	3.74%
CLASS A | Return After Taxes on Distributions	[1]	1.83%	2.26%	3.71%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	2.33%	2.48%	3.72%
CLASS B		1.33%	2.17%	3.63%
CLASS C		3.32%	2.17%	3.33%
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ----- .78% 1.53% 1.53%

[5] This expense information differs from the Portfolio's most recent annual report.

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND II | AB Arizona Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB ARIZONA PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and State of Arizona personal income tax that is available without assuming what the Adviser considers to be undue risk.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	SHAREHOLDER FEES (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 12% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	12.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Arizona or municipal securities with interest that is otherwise exempt from Arizona state income tax. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Arizona municipal securities are vulnerable to events adversely affecting its economy. The leading sectors of Arizona's economy are the real estate and rental industries, tourism and wholesale trade. Construction is also an important sector due to the rapid growth of Arizona's population in recent years. These sectors are particularly vulnerable to times of impaired consumer and business spending. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li> how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.08%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 5.95%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -3.70%, 4TH QUARTER, 2010.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br />AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND II | AB Arizona Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.25%
Total Other Expenses	rr_OtherExpensesOverAssets	0.30%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.00%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.21%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.79%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 378
After 3 Years	rr_ExpenseExampleYear03	589
After 5 Years	rr_ExpenseExampleYear05	816
After 10 Years	rr_ExpenseExampleYear10	$ 1,469
2008	rr_AnnualReturn2008	(5.20%)
2009	rr_AnnualReturn2009	14.12%
2010	rr_AnnualReturn2010	2.17%
2011	rr_AnnualReturn2011	9.21%
2012	rr_AnnualReturn2012	6.88%
2013	rr_AnnualReturn2013	(3.36%)
2014	rr_AnnualReturn2014	8.83%
2015	rr_AnnualReturn2015	3.55%
2016	rr_AnnualReturn2016	0.86%
2017	rr_AnnualReturn2017	5.01%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.08%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.95%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.70%)
1 YEAR	rr_AverageAnnualReturnYear01	1.85%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.28%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.74%	[5]
AB MUNICIPAL INCOME FUND II | AB Arizona 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	3.00%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	none
Other Expenses	rr_Component3OtherExpensesOverAssets	0.24%
Total Other Expenses	rr_OtherExpensesOverAssets	0.29%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.74%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.21%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.53%	[3],[4],[7]
After 1 Year	rr_ExpenseExampleYear01	$ 456
After 3 Years	rr_ExpenseExampleYear03	628
After 5 Years	rr_ExpenseExampleYear05	924
After 10 Years	rr_ExpenseExampleYear10	1,658
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	156
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	528
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	924
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,658
1 YEAR	rr_AverageAnnualReturnYear01	1.33%
5 YEARS	rr_AverageAnnualReturnYear05	2.17%
10 YEARS	rr_AverageAnnualReturnYear10	3.63%
AB MUNICIPAL INCOME FUND II | AB Arizona 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%	[8]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.25%
Total Other Expenses	rr_OtherExpensesOverAssets	0.30%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.75%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.21%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.54%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 257
After 3 Years	rr_ExpenseExampleYear03	531
After 5 Years	rr_ExpenseExampleYear05	929
After 10 Years	rr_ExpenseExampleYear10	2,045
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	157
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	531
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	929
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,045
1 YEAR	rr_AverageAnnualReturnYear01	3.32%
5 YEARS	rr_AverageAnnualReturnYear05	2.17%
10 YEARS	rr_AverageAnnualReturnYear10	3.33%
AB MUNICIPAL INCOME FUND II | AB Arizona Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	1.83%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.26%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.71%	[5]
AB MUNICIPAL INCOME FUND II | AB Arizona Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.33%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.48%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.72%	[5]
AB MUNICIPAL INCOME FUND II | AB Arizona Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ----- .78% 1.53% 1.53%

[5] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[6] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[7] This expense information differs from the Portfolio's most recent annual report.

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

XML

AB MUNICIPAL INCOME FUND II | AB Massachusetts Portfolio

AB MASSACHUSETTS PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and Commonwealth of Massachusetts personal income tax that is available without assuming what the Adviser considers to be undue risk.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 MUNICIPAL INCOME FUND II - AB Massachusetts Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES		ADVISOR CLASS SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]	none
Exchange Fee	none	none		none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND II - AB Massachusetts Portfolio		CLASS A	CLASS B	CLASS C	ADVISOR CLASS
Management Fees		0.45%	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none
Other Expenses: Transfer Agent		0.03%	0.06%	0.03%	0.03%
Other Expenses: Interest Expense		0.01%	0.01%	0.01%	0.02%
Other Expenses		0.15%	0.14%	0.15%	0.14%
Total Other Expenses		0.19%	0.21%	0.19%	0.19%
Total Annual Portfolio Operating Expenses	[1]	0.89%	1.66%	1.64%	0.64%
Fee Waiver and/or Expense Reimbursement	[2]	(0.11%)	(0.13%)	(0.11%)	(0.10%)
Total Annual Portfolio Operating Expenses	[3],[4]	0.78%	1.53%	1.53%	0.54%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND II - AB Massachusetts Portfolio - USD ($)	CLASS A	CLASS B	CLASS C	ADVISOR CLASS
After 1 Year	$ 377	$ 456	$ 256	$ 55
After 3 Years	565	611	507	195
After 5 Years	768	890	881	347
After 10 Years	$ 1,353	$ 1,560	$ 1,934	$ 789

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 MUNICIPAL INCOME FUND II - AB Massachusetts Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 156	$ 156
After 3 Years	511	507
After 5 Years	890	881
After 10 Years	$ 1,560	$ 1,934

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 19% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Massachusetts or municipal securities with interest that is otherwise exempt from Massachusetts state income tax.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Massachusetts municipal securities are vulnerable to events adversely affecting its economy, which is relatively diverse and based on education, healthcare, financial services, real estate and high technology. Massachusetts has a high degree of job stability and an educated work force due to its large concentration of colleges and universities but the high cost of doing business in Massachusetts may serve as an impediment to job creation. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.52%.

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

BEST QUARTER WAS UP 5.76%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.70%, 4TH QUARTER, 2010.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND II - AB Massachusetts Portfolio		1 YEAR	5 YEARS	10 YEARS	INCEPTION DATE
CLASS A	[1]	1.39%	1.67%	3.73%
CLASS A | Return After Taxes on Distributions	[1]	1.31%	1.61%	3.67%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	2.06%	1.95%	3.64%
CLASS B		0.72%	1.56%	3.62%
CLASS C		2.71%	1.56%	3.32%
ADVISOR CLASS	[2]	4.75%	2.54%	4.30%	Jul. 25, 2016
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ADVISOR CLASS ----- .77% 1.52% 1.52% .52%

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[2] Inception Date for Advisor Class shares: 7/25/2016. Performance information for periods prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND II | AB Massachusetts Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB MASSACHUSETTS PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and Commonwealth of Massachusetts personal income tax that is available without assuming what the Adviser considers to be undue risk.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 19% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	19.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Massachusetts or municipal securities with interest that is otherwise exempt from Massachusetts state income tax. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Massachusetts municipal securities are vulnerable to events adversely affecting its economy, which is relatively diverse and based on education, healthcare, financial services, real estate and high technology. Massachusetts has a high degree of job stability and an educated work force due to its large concentration of colleges and universities but the high cost of doing business in Massachusetts may serve as an impediment to job creation. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li>how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.52%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 5.76%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.70%, 4TH QUARTER, 2010.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND II | AB Massachusetts Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.15%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.89%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.78%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 377
After 3 Years	rr_ExpenseExampleYear03	565
After 5 Years	rr_ExpenseExampleYear05	768
After 10 Years	rr_ExpenseExampleYear10	$ 1,353
2008	rr_AnnualReturn2008	(1.64%)
2009	rr_AnnualReturn2009	10.96%
2010	rr_AnnualReturn2010	1.84%
2011	rr_AnnualReturn2011	10.94%
2012	rr_AnnualReturn2012	7.65%
2013	rr_AnnualReturn2013	(4.29%)
2014	rr_AnnualReturn2014	8.34%
2015	rr_AnnualReturn2015	3.35%
2016	rr_AnnualReturn2016	0.04%
2017	rr_AnnualReturn2017	4.48%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.52%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.76%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.70%)
1 YEAR	rr_AverageAnnualReturnYear01	1.39%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	1.67%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.73%	[5]
AB MUNICIPAL INCOME FUND II | AB Massachusetts 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	3.00%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.06%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.14%
Total Other Expenses	rr_OtherExpensesOverAssets	0.21%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.66%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.13%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.53%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 456
After 3 Years	rr_ExpenseExampleYear03	611
After 5 Years	rr_ExpenseExampleYear05	890
After 10 Years	rr_ExpenseExampleYear10	1,560
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	156
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	511
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	890
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,560
1 YEAR	rr_AverageAnnualReturnYear01	0.72%
5 YEARS	rr_AverageAnnualReturnYear05	1.56%
10 YEARS	rr_AverageAnnualReturnYear10	3.62%
AB MUNICIPAL INCOME FUND II | AB Massachusetts 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%	[7]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.15%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.64%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.53%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 256
After 3 Years	rr_ExpenseExampleYear03	507
After 5 Years	rr_ExpenseExampleYear05	881
After 10 Years	rr_ExpenseExampleYear10	1,934
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	156
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	507
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	881
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,934
1 YEAR	rr_AverageAnnualReturnYear01	2.71%
5 YEARS	rr_AverageAnnualReturnYear05	1.56%
10 YEARS	rr_AverageAnnualReturnYear10	3.32%
AB MUNICIPAL INCOME FUND II | AB Massachusetts 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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.03%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.02%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.14%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.64%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.10%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.54%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 55
After 3 Years	rr_ExpenseExampleYear03	195
After 5 Years	rr_ExpenseExampleYear05	347
After 10 Years	rr_ExpenseExampleYear10	$ 789
1 YEAR	rr_AverageAnnualReturnYear01	4.75%	[8]
5 YEARS	rr_AverageAnnualReturnYear05	2.54%	[8]
10 YEARS	rr_AverageAnnualReturnYear10	4.30%	[8]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jul. 25, 2016	[8]
AB MUNICIPAL INCOME FUND II | AB Massachusetts Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	1.31%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	1.61%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.67%	[5]
AB MUNICIPAL INCOME FUND II | AB Massachusetts Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.06%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	1.95%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.64%	[5]
AB MUNICIPAL INCOME FUND II | AB Massachusetts Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ADVISOR CLASS ----- .77% 1.52% 1.52% .52%

[5] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[6] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

[8] Inception Date for Advisor Class shares: 7/25/2016. Performance information for periods prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

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AB MUNICIPAL INCOME FUND II | AB Minnesota Portfolio

AB MINNESOTA PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and State of Minnesota personal income tax that is available without assuming what the Adviser considers to be undue risk.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB MUNICIPAL INCOME FUND II - AB Minnesota Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]
Exchange Fee	none	none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND II - AB Minnesota Portfolio		CLASS A	CLASS B	CLASS C
Management Fees		0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%
Other Expenses: Transfer Agent		0.06%	0.12%	0.06%
Other Expenses: Interest Expense		0.01%	0.01%	0.01%
Other Expenses		0.40%	0.40%	0.40%
Total Other Expenses		0.47%	0.53%	0.47%
Total Annual Portfolio Operating Expenses	[1]	1.17%	1.98%	1.92%
Fee Waiver and/or Expense Reimbursement	[2]	(0.31%)	(0.37%)	(0.31%)
Total Annual Portfolio Operating Expenses	[3],[4]	0.86%	1.61%	1.61%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND II - AB Minnesota Portfolio - USD ($)	CLASS A	CLASS B	CLASS C
After 1 Year	$ 385	$ 464	$ 264
After 3 Years	631	686	573
After 5 Years	895	1,033	1,008
After 10 Years	$ 1,651	$ 1,873	$ 2,218

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 MUNICIPAL INCOME FUND II - AB Minnesota Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 164	$ 164
After 3 Years	586	573
After 5 Years	1,033	1,008
After 10 Years	$ 1,873	$ 2,218

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 16% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Minnesota or municipal securities with interest that is otherwise exempt from Minnesota state income tax.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Minnesota municipal securities may be vulnerable to events adversely affecting its economy. Minnesota's economy is diverse, but there are employment concentrations in the fabricated metals, machinery, computers and electronics categories of the durable goods sector and construction, which are vulnerable during general economic downturns. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.59%.

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

BEST QUARTER WAS UP 6.19%, 1ST QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.03%, 4TH QUARTER, 2010.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND II - AB Minnesota Portfolio		1 YEAR	5 YEARS	10 YEARS
CLASS A	[1]	1.36%	1.85%	3.38%
CLASS A | Return After Taxes on Distributions	[1]	1.33%	1.75%	3.31%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	1.99%	2.05%	3.32%
CLASS B		0.67%	1.75%	3.26%
CLASS C		2.67%	1.72%	2.96%
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Including Interest Expense Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ----- .85% 1.60% 1.60%

[4] Including Interest Expense After Fee Waiver and/or Expense Reimbursement

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND II | AB Minnesota Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB MINNESOTA PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and State of Minnesota personal income tax that is available without assuming what the Adviser considers to be undue risk.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	SHAREHOLDER FEES (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 16% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	16.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Minnesota or municipal securities with interest that is otherwise exempt from Minnesota state income tax. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Minnesota municipal securities may be vulnerable to events adversely affecting its economy. Minnesota's economy is diverse, but there are employment concentrations in the fabricated metals, machinery, computers and electronics categories of the durable goods sector and construction, which are vulnerable during general economic downturns. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li>how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.59%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 6.19%, 1ST QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.03%, 4TH QUARTER, 2010.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/> AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND II | AB Minnesota Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.06%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.40%
Total Other Expenses	rr_OtherExpensesOverAssets	0.47%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.17%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.31%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.86%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 385
After 3 Years	rr_ExpenseExampleYear03	631
After 5 Years	rr_ExpenseExampleYear05	895
After 10 Years	rr_ExpenseExampleYear10	$ 1,651
2008	rr_AnnualReturn2008	(3.55%)
2009	rr_AnnualReturn2009	11.66%
2010	rr_AnnualReturn2010	1.25%
2011	rr_AnnualReturn2011	10.39%
2012	rr_AnnualReturn2012	5.65%
2013	rr_AnnualReturn2013	(2.82%)
2014	rr_AnnualReturn2014	8.00%
2015	rr_AnnualReturn2015	2.57%
2016	rr_AnnualReturn2016	0.46%
2017	rr_AnnualReturn2017	4.46%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.59%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.19%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.03%)
1 YEAR	rr_AverageAnnualReturnYear01	1.36%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	1.85%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.38%	[5]
AB MUNICIPAL INCOME FUND II | AB Minnesota 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	3.00%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.12%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.40%
Total Other Expenses	rr_OtherExpensesOverAssets	0.53%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.98%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.37%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.61%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 464
After 3 Years	rr_ExpenseExampleYear03	686
After 5 Years	rr_ExpenseExampleYear05	1,033
After 10 Years	rr_ExpenseExampleYear10	1,873
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	164
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	586
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,033
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,873
1 YEAR	rr_AverageAnnualReturnYear01	0.67%
5 YEARS	rr_AverageAnnualReturnYear05	1.75%
10 YEARS	rr_AverageAnnualReturnYear10	3.26%
AB MUNICIPAL INCOME FUND II | AB Minnesota 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%	[7]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.06%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.40%
Total Other Expenses	rr_OtherExpensesOverAssets	0.47%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.92%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.31%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.61%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 264
After 3 Years	rr_ExpenseExampleYear03	573
After 5 Years	rr_ExpenseExampleYear05	1,008
After 10 Years	rr_ExpenseExampleYear10	2,218
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	164
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	573
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,008
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,218
1 YEAR	rr_AverageAnnualReturnYear01	2.67%
5 YEARS	rr_AverageAnnualReturnYear05	1.72%
10 YEARS	rr_AverageAnnualReturnYear10	2.96%
AB MUNICIPAL INCOME FUND II | AB Minnesota Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	1.33%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	1.75%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.31%	[5]
AB MUNICIPAL INCOME FUND II | AB Minnesota Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	1.99%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.05%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.32%	[5]
AB MUNICIPAL INCOME FUND II | AB Minnesota Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Including Interest Expense Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ----- .85% 1.60% 1.60%

[4] Including Interest Expense After Fee Waiver and/or Expense Reimbursement

[5] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[6] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

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AB MUNICIPAL INCOME FUND II | AB New Jersey Portfolio

AB NEW JERSEY PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and State of New Jersey personal income tax that is available without assuming what the Adviser considers to be undue risk.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").

SHAREHOLDER FEES (fees paid directly from your investment)

Shareholder Fees - AB MUNICIPAL INCOME FUND II - AB New Jersey Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]
Exchange Fee	none	none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND II - AB New Jersey Portfolio		CLASS A	CLASS B	CLASS C
Management Fees		0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%
Other Expenses: Transfer Agent		0.05%	0.05%	0.05%
Other Expenses: Interest Expense		0.01%	0.01%	0.01%
Other Expenses		0.27%	0.27%	0.26%
Total Other Expenses		0.33%	0.33%	0.32%
Total Annual Portfolio Operating Expenses	[1]	1.03%	1.78%	1.77%
Fee Waiver and/or Expense Reimbursement	[2]	(0.20%)	(0.20%)	(0.19%)
Total Annual Portfolio Operating Expenses	[3],[4]	0.83%	1.58%	1.58%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND II - AB New Jersey Portfolio - USD ($)	CLASS A	CLASS B	CLASS C
After 1 Year	$ 382	$ 461	$ 261
After 3 Years	599	641	539
After 5 Years	833	946	942
After 10 Years	$ 1,504	$ 1,698	$ 2,068

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 MUNICIPAL INCOME FUND II - AB New Jersey Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 161	$ 161
After 3 Years	541	539
After 5 Years	946	942
After 10 Years	$ 1,698	$ 2,068

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 26% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of New Jersey or municipal securities with interest that is otherwise exempt from New Jersey state income tax.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in New Jersey municipal securities may be vulnerable to events adversely affecting its economy. New Jersey's economy is a diverse mix of manufacturing, construction, and service industries, supplemented by rural areas with selective commercial agriculture. Major components of its economy are financial services and pharmaceuticals and adverse events affecting these industries will have a negative effect on New Jersey's economy. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.48%.

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

BEST QUARTER WAS UP 6.76%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -3.99%, 4TH QUARTER, 2008.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND II - AB New Jersey Portfolio		1 YEAR	5 YEARS	10 YEARS
CLASS A	[1]	3.30%	2.13%	3.64%
CLASS A | Return After Taxes on Distributions	[1]	3.30%	2.09%	3.61%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	3.28%	2.37%	3.64%
CLASS B		2.69%	2.01%	3.53%
CLASS C		4.54%	1.99%	3.22%
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ----- .82% 1.57% 1.57%

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

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Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND II | AB New Jersey Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB NEW JERSEY PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and State of New Jersey personal income tax that is available without assuming what the Adviser considers to be undue risk.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	SHAREHOLDER FEES (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 26% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	26.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of New Jersey or municipal securities with interest that is otherwise exempt from New Jersey state income tax. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in New Jersey municipal securities may be vulnerable to events adversely affecting its economy. New Jersey's economy is a diverse mix of manufacturing, construction, and service industries, supplemented by rural areas with selective commercial agriculture. Major components of its economy are financial services and pharmaceuticals and adverse events affecting these industries will have a negative effect on New Jersey's economy. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li>how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.48%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 6.76%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -3.99%, 4TH QUARTER, 2008.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br />AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND II | AB New Jersey Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.27%
Total Other Expenses	rr_OtherExpensesOverAssets	0.33%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.03%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.20%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.83%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 382
After 3 Years	rr_ExpenseExampleYear03	599
After 5 Years	rr_ExpenseExampleYear05	833
After 10 Years	rr_ExpenseExampleYear10	$ 1,504
2008	rr_AnnualReturn2008	(6.84%)
2009	rr_AnnualReturn2009	13.97%
2010	rr_AnnualReturn2010	3.34%
2011	rr_AnnualReturn2011	9.34%
2012	rr_AnnualReturn2012	7.37%
2013	rr_AnnualReturn2013	(3.84%)
2014	rr_AnnualReturn2014	7.74%
2015	rr_AnnualReturn2015	3.03%
2016	rr_AnnualReturn2016	0.75%
2017	rr_AnnualReturn2017	6.45%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.48%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.76%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.99%)
1 YEAR	rr_AverageAnnualReturnYear01	3.30%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.13%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.64%	[5]
AB MUNICIPAL INCOME FUND II | AB New Jersey 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	3.00%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.27%
Total Other Expenses	rr_OtherExpensesOverAssets	0.33%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.78%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.20%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.58%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 461
After 3 Years	rr_ExpenseExampleYear03	641
After 5 Years	rr_ExpenseExampleYear05	946
After 10 Years	rr_ExpenseExampleYear10	1,698
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	161
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	541
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	946
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,698
1 YEAR	rr_AverageAnnualReturnYear01	2.69%
5 YEARS	rr_AverageAnnualReturnYear05	2.01%
10 YEARS	rr_AverageAnnualReturnYear10	3.53%
AB MUNICIPAL INCOME FUND II | AB New Jersey 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%	[7]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.26%
Total Other Expenses	rr_OtherExpensesOverAssets	0.32%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.77%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.19%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.58%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 261
After 3 Years	rr_ExpenseExampleYear03	539
After 5 Years	rr_ExpenseExampleYear05	942
After 10 Years	rr_ExpenseExampleYear10	2,068
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	161
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	539
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	942
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,068
1 YEAR	rr_AverageAnnualReturnYear01	4.54%
5 YEARS	rr_AverageAnnualReturnYear05	1.99%
10 YEARS	rr_AverageAnnualReturnYear10	3.22%
AB MUNICIPAL INCOME FUND II | AB New Jersey Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	3.30%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.09%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.61%	[5]
AB MUNICIPAL INCOME FUND II | AB New Jersey Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	3.28%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.37%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.64%	[5]
AB MUNICIPAL INCOME FUND II | AB New Jersey Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ----- .82% 1.57% 1.57%

[5] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[6] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

XML

AB MUNICIPAL INCOME FUND, INC. | AB New York Portfolio

AB NEW YORK PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and New York State and City income tax that is available without assuming what the Adviser considers to be undue risk to principal or income.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 MUNICIPAL INCOME FUND, INC. - AB New York Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES		ADVISOR CLASS SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]	none
Exchange Fee	none	none		none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND, INC. - AB New York Portfolio		CLASS A	CLASS B	CLASS C	ADVISOR CLASS
Management Fees		0.45%	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none
Other Expenses: Transfer Agent		0.04%	0.04%	0.04%	0.04%
Other Expenses		0.07%	0.07%	0.07%	0.07%
Total Other Expenses		0.11%	0.11%	0.11%	0.11%
Total Annual Portfolio Operating Expenses	[1]	0.81%	1.56%	1.56%	0.56%
Fee Waiver and/or Expense Reimbursement	[2]	(0.06%)	(0.06%)	(0.06%)	(0.06%)
Total Annual Portfolio Operating Expenses	[3]	0.75%	1.50%	1.50%	0.50%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND, INC. - AB New York Portfolio - USD ($)	CLASS A	CLASS B	CLASS C	ADVISOR CLASS
After 1 Year	$ 374	$ 453	$ 253	$ 51
After 3 Years	545	587	487	173
After 5 Years	730	844	844	307
After 10 Years	$ 1,266	$ 1,464	$ 1,851	$ 696

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 MUNICIPAL INCOME FUND, INC. - AB New York Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 153	$ 153
After 3 Years	487	487
After 5 Years	844	844
After 10 Years	$ 1,464	$ 1,851

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 11% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of New York or municipal securities with interest that is otherwise exempt from New York state income tax.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in New York municipal securities may be vulnerable to events adversely affecting its economy. New York's economy, while diverse, has a relatively large share of the nation's financial activities. With the financial services sector contributing about one-fifth of the state's wages, the state's economy is especially vulnerable to adverse events affecting the financial markets such as those that occurred in 2008-2009. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.57%.

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

BEST QUARTER WAS UP 6.36%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.00%, 4TH QUARTER, 2016.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND, INC. - AB New York Portfolio		1 YEAR	5 YEARS	10 YEARS	INCEPTION DATE
CLASS A	[1]	2.32%	1.76%	3.47%
CLASS A | Return After Taxes on Distributions	[1]	2.32%	1.75%	3.46%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	2.57%	2.04%	3.46%
CLASS B		1.69%	1.64%	3.36%
CLASS C		3.58%	1.61%	3.05%
ADVISOR CLASS	[2]	5.63%	2.65%	4.08%	Aug. 06, 2008
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Including Interest Expense Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] Including Interest Expense After Fee Waiver and/or Expense Reimbursement

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[2] Inception date for Advisor Class shares: 8/6/08. Performance information for periods prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND, INC. | AB New York Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB NEW YORK PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and New York State and City income tax that is available without assuming what the Adviser considers to be undue risk to principal or income.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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 PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 11% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	11.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of New York or municipal securities with interest that is otherwise exempt from New York state income tax. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in New York municipal securities may be vulnerable to events adversely affecting its economy. New York's economy, while diverse, has a relatively large share of the nation's financial activities. With the financial services sector contributing about one-fifth of the state's wages, the state's economy is especially vulnerable to adverse events affecting the financial markets such as those that occurred in 2008-2009. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and </li></ul><ul type="square"><li>how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.57%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 6.36%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.00%, 4TH QUARTER, 2016.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND, INC. | AB New York Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.07%
Total Other Expenses	rr_OtherExpensesOverAssets	0.11%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.81%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.75%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 374
After 3 Years	rr_ExpenseExampleYear03	545
After 5 Years	rr_ExpenseExampleYear05	730
After 10 Years	rr_ExpenseExampleYear10	$ 1,266
2008	rr_AnnualReturn2008	(4.69%)
2009	rr_AnnualReturn2009	13.00%
2010	rr_AnnualReturn2010	2.67%
2011	rr_AnnualReturn2011	9.56%
2012	rr_AnnualReturn2012	6.41%
2013	rr_AnnualReturn2013	(4.50%)
2014	rr_AnnualReturn2014	8.15%
2015	rr_AnnualReturn2015	3.13%
2016	rr_AnnualReturn2016	0.11%
2017	rr_AnnualReturn2017	5.47%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.57%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.36%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2016
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.00%)
1 YEAR	rr_AverageAnnualReturnYear01	2.32%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	1.76%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.47%	[4]
AB MUNICIPAL INCOME FUND, INC. | AB New York 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	3.00%	[5]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.07%
Total Other Expenses	rr_OtherExpensesOverAssets	0.11%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.56%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.50%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 453
After 3 Years	rr_ExpenseExampleYear03	587
After 5 Years	rr_ExpenseExampleYear05	844
After 10 Years	rr_ExpenseExampleYear10	1,464
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	153
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	487
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	844
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,464
1 YEAR	rr_AverageAnnualReturnYear01	1.69%
5 YEARS	rr_AverageAnnualReturnYear05	1.64%
10 YEARS	rr_AverageAnnualReturnYear10	3.36%
AB MUNICIPAL INCOME FUND, INC. | AB New York 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%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.07%
Total Other Expenses	rr_OtherExpensesOverAssets	0.11%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.56%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.50%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 253
After 3 Years	rr_ExpenseExampleYear03	487
After 5 Years	rr_ExpenseExampleYear05	844
After 10 Years	rr_ExpenseExampleYear10	1,851
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	153
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	487
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	844
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,851
1 YEAR	rr_AverageAnnualReturnYear01	3.58%
5 YEARS	rr_AverageAnnualReturnYear05	1.61%
10 YEARS	rr_AverageAnnualReturnYear10	3.05%
AB MUNICIPAL INCOME FUND, INC. | AB New York 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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.07%
Total Other Expenses	rr_OtherExpensesOverAssets	0.11%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.56%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.06%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.50%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 51
After 3 Years	rr_ExpenseExampleYear03	173
After 5 Years	rr_ExpenseExampleYear05	307
After 10 Years	rr_ExpenseExampleYear10	$ 696
1 YEAR	rr_AverageAnnualReturnYear01	5.63%	[7]
5 YEARS	rr_AverageAnnualReturnYear05	2.65%	[7]
10 YEARS	rr_AverageAnnualReturnYear10	4.08%	[7]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Aug. 06, 2008	[7]
AB MUNICIPAL INCOME FUND, INC. | AB New York Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.32%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	1.75%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.46%	[4]
AB MUNICIPAL INCOME FUND, INC. | AB New York Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.57%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	2.04%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.46%	[4]
AB MUNICIPAL INCOME FUND, INC. | AB New York Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Including Interest Expense Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] Including Interest Expense After Fee Waiver and/or Expense Reimbursement

[4] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[5] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

[7] Inception date for Advisor Class shares: 8/6/08. Performance information for periods prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

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AB MUNICIPAL INCOME FUND II | AB Ohio Portfolio

AB OHIO PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and State of Ohio personal income tax that is available without assuming what the Adviser considers to be undue risk.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").

SHAREHOLDER FEES (fees paid directly from your investment) <!-- $$/page= -->

Shareholder Fees - AB MUNICIPAL INCOME FUND II - AB Ohio Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]
Exchange Fee	none	none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND II - AB Ohio Portfolio		CLASS A	CLASS B	CLASS C
Management Fees		0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%
Other Expenses: Transfer Agent		0.05%	0.10%	0.05%
Other Expenses		0.32%	0.31%	0.32%
Total Other Expenses		0.37%	0.41%	0.37%
Total Annual Portfolio Operating Expenses	[1]	1.07%	1.86%	1.82%
Fee Waiver and/or Expense Reimbursement	[2]	(0.27%)	(0.31%)	(0.27%)
Total Annual Portfolio Operating Expenses	[3]	0.80%	1.55%	1.55%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND II - AB Ohio Portfolio - USD ($)	CLASS A	CLASS B	CLASS C
After 1 Year	$ 379	$ 458	$ 258
After 3 Years	604	655	546
After 5 Years	847	977	960
After 10 Years	$ 1,543	$ 1,757	$ 2,115

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 MUNICIPAL INCOME FUND II - AB Ohio Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 158	$ 158
After 3 Years	555	546
After 5 Years	977	960
After 10 Years	$ 1,757	$ 2,115

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 12% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Ohio or municipal securities with interest that is otherwise exempt from Ohio state income tax.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Ohio municipal securities may be vulnerable to events adversely affecting its economy. Ohio's economy is heavily reliant on manufacturing, particularly the automobile and related products industries, which were severely affected by the downturn in economic conditions in 2008-2009 but have since recovered, but the greatest growth in Ohio's economy in recent years has been in the non-manufacturing sectors. Adverse economic conditions can adversely affect the state's economy and employment rates. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.30%.

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

BEST QUARTER WAS UP 5.82%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -3.44%, 4TH QUARTER, 2016.  

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND II - AB Ohio Portfolio		1 YEAR	5 YEARS	10 YEARS
CLASS A	[1]	1.78%	1.54%	3.24%
CLASS A | Return After Taxes on Distributions	[1]	1.77%	1.50%	3.20%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	2.20%	1.84%	3.26%
CLASS B		1.23%	1.43%	3.12%
CLASS C		3.21%	1.43%	2.83%
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND II | AB Ohio Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB OHIO PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and State of Ohio personal income tax that is available without assuming what the Adviser considers to be undue risk.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	SHAREHOLDER FEES (fees paid directly from your investment) <!-- $$/page= -->
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 12% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	12.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Ohio or municipal securities with interest that is otherwise exempt from Ohio state income tax. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Ohio municipal securities may be vulnerable to events adversely affecting its economy. Ohio's economy is heavily reliant on manufacturing, particularly the automobile and related products industries, which were severely affected by the downturn in economic conditions in 2008-2009 but have since recovered, but the greatest growth in Ohio's economy in recent years has been in the non-manufacturing sectors. Adverse economic conditions can adversely affect the state's economy and employment rates. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li>how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.30%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 5.82%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -3.44%, 4TH QUARTER, 2016.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.<br />
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;<br />
AB MUNICIPAL INCOME FUND II | AB Ohio Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.32%
Total Other Expenses	rr_OtherExpensesOverAssets	0.37%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.07%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.27%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.80%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 379
After 3 Years	rr_ExpenseExampleYear03	604
After 5 Years	rr_ExpenseExampleYear05	847
After 10 Years	rr_ExpenseExampleYear10	$ 1,543
2008	rr_AnnualReturn2008	(3.99%)
2009	rr_AnnualReturn2009	11.94%
2010	rr_AnnualReturn2010	3.37%
2011	rr_AnnualReturn2011	7.99%
2012	rr_AnnualReturn2012	6.14%
2013	rr_AnnualReturn2013	(5.42%)
2014	rr_AnnualReturn2014	7.95%
2015	rr_AnnualReturn2015	3.41%
2016	rr_AnnualReturn2016	0.51%
2017	rr_AnnualReturn2017	4.89%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.30%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.82%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2016
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.44%)
1 YEAR	rr_AverageAnnualReturnYear01	1.78%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	1.54%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.24%	[4]
AB MUNICIPAL INCOME FUND II | AB Ohio 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	3.00%	[5]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.10%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.31%
Total Other Expenses	rr_OtherExpensesOverAssets	0.41%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.86%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.31%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.55%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 458
After 3 Years	rr_ExpenseExampleYear03	655
After 5 Years	rr_ExpenseExampleYear05	977
After 10 Years	rr_ExpenseExampleYear10	1,757
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	158
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	555
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	977
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,757
1 YEAR	rr_AverageAnnualReturnYear01	1.23%
5 YEARS	rr_AverageAnnualReturnYear05	1.43%
10 YEARS	rr_AverageAnnualReturnYear10	3.12%
AB MUNICIPAL INCOME FUND II | AB Ohio 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%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.05%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.32%
Total Other Expenses	rr_OtherExpensesOverAssets	0.37%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.82%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.27%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.55%	[3]
After 1 Year	rr_ExpenseExampleYear01	$ 258
After 3 Years	rr_ExpenseExampleYear03	546
After 5 Years	rr_ExpenseExampleYear05	960
After 10 Years	rr_ExpenseExampleYear10	2,115
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	158
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	546
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	960
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,115
1 YEAR	rr_AverageAnnualReturnYear01	3.21%
5 YEARS	rr_AverageAnnualReturnYear05	1.43%
10 YEARS	rr_AverageAnnualReturnYear10	2.83%
AB MUNICIPAL INCOME FUND II | AB Ohio Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	1.77%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	1.50%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.20%	[4]
AB MUNICIPAL INCOME FUND II | AB Ohio Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.20%	[4]
5 YEARS	rr_AverageAnnualReturnYear05	1.84%	[4]
10 YEARS	rr_AverageAnnualReturnYear10	3.26%	[4]
AB MUNICIPAL INCOME FUND II | AB Ohio Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[5] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

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AB MUNICIPAL INCOME FUND II | AB Pennsylvania Portfolio

AB PENNSYLVANIA PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and Commonwealth of Pennsylvania personal income tax that is available without assuming what the Adviser considers to be undue risk.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").

SHAREHOLDER FEES (fees paid directly from your investment) <!-- $$/page= -->

Shareholder Fees - AB MUNICIPAL INCOME FUND II - AB Pennsylvania Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]
Exchange Fee	none	none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND II - AB Pennsylvania Portfolio		CLASS A	CLASS B	CLASS C
Management Fees		0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%
Other Expenses: Transfer Agent		0.06%	0.13%	0.06%
Other Expenses: Interest Expense		0.01%	0.01%	0.01%
Other Expenses		0.32%	0.32%	0.32%
Total Other Expenses		0.39%	0.46%	0.39%
Total Annual Portfolio Operating Expenses	[1]	1.09%	1.91%	1.84%
Fee Waiver and/or Expense Reimbursement	[2]	(0.23%)	(0.30%)	(0.23%)
Total Annual Portfolio Operating Expenses	[3],[4]	0.86%	1.61%	1.61%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND II - AB Pennsylvania Portfolio - USD ($)	CLASS A	CLASS B	CLASS C
After 1 Year	$ 385	$ 464	$ 264
After 3 Years	614	671	556
After 5 Years	861	1,004	974
After 10 Years	$ 1,569	$ 1,798	$ 2,140

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 MUNICIPAL INCOME FUND II - AB Pennsylvania Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 164	$ 164
After 3 Years	571	556
After 5 Years	1,004	974
After 10 Years	$ 1,798	$ 2,140

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 38% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Pennsylvania or municipal securities with interest that is otherwise exempt from Pennsylvania state income tax.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Pennsylvania municipal securities may be vulnerable to events adversely affecting its economy. Pennsylvania's economy has become more diverse, shifting from the coal, steel, and railroad industries. Currently, the major sources of growth in Pennsylvania are in the service sector, including trade, medical and health services, education and financial institutions. However, the state is vulnerable to business downturns and decreased capital spending. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.26%.

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

BEST QUARTER WAS UP 6.86%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.16%, 4TH QUARTER, 2008.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND II - AB Pennsylvania Portfolio		1 YEAR	5 YEARS	10 YEARS
CLASS A	[1]	2.09%	2.04%	3.54%
CLASS A | Return After Taxes on Distributions	[1]	2.09%	2.01%	3.49%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	2.45%	2.24%	3.51%
CLASS B		1.58%	1.93%	3.43%
CLASS C		3.57%	1.93%	3.13%
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ----- .85% 1.60% 1.60%

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND II | AB Pennsylvania Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB PENNSYLVANIA PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and Commonwealth of Pennsylvania personal income tax that is available without assuming what the Adviser considers to be undue risk.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio's Statement of Additional Information ("SAI").
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	SHAREHOLDER FEES (fees paid directly from your investment) <!-- $$/page= -->
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 38% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	38.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Pennsylvania or municipal securities with interest that is otherwise exempt from Pennsylvania state income tax. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Pennsylvania municipal securities may be vulnerable to events adversely affecting its economy. Pennsylvania's economy has become more diverse, shifting from the coal, steel, and railroad industries. Currently, the major sources of growth in Pennsylvania are in the service sector, including trade, medical and health services, education and financial institutions. However, the state is vulnerable to business downturns and decreased capital spending. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li> how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.26%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 6.86%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.16%, 4TH QUARTER, 2008.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br />AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND II | AB Pennsylvania Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.06%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.32%
Total Other Expenses	rr_OtherExpensesOverAssets	0.39%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.09%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.23%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.86%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 385
After 3 Years	rr_ExpenseExampleYear03	614
After 5 Years	rr_ExpenseExampleYear05	861
After 10 Years	rr_ExpenseExampleYear10	$ 1,569
2008	rr_AnnualReturn2008	(7.49%)
2009	rr_AnnualReturn2009	14.44%
2010	rr_AnnualReturn2010	3.46%
2011	rr_AnnualReturn2011	9.77%
2012	rr_AnnualReturn2012	6.51%
2013	rr_AnnualReturn2013	(4.07%)
2014	rr_AnnualReturn2014	8.93%
2015	rr_AnnualReturn2015	3.21%
2016	rr_AnnualReturn2016	0.42%
2017	rr_AnnualReturn2017	5.27%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.26%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	6.86%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.16%)
1 YEAR	rr_AverageAnnualReturnYear01	2.09%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.04%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.54%	[5]
AB MUNICIPAL INCOME FUND II | AB Pennsylvania 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	3.00%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.13%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.32%
Total Other Expenses	rr_OtherExpensesOverAssets	0.46%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.91%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.30%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.61%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 464
After 3 Years	rr_ExpenseExampleYear03	671
After 5 Years	rr_ExpenseExampleYear05	1,004
After 10 Years	rr_ExpenseExampleYear10	1,798
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	164
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	571
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	1,004
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,798
1 YEAR	rr_AverageAnnualReturnYear01	1.58%
5 YEARS	rr_AverageAnnualReturnYear05	1.93%
10 YEARS	rr_AverageAnnualReturnYear10	3.43%
AB MUNICIPAL INCOME FUND II | AB Pennsylvania 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%	[7]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.06%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.32%
Total Other Expenses	rr_OtherExpensesOverAssets	0.39%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.84%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.23%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.61%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 264
After 3 Years	rr_ExpenseExampleYear03	556
After 5 Years	rr_ExpenseExampleYear05	974
After 10 Years	rr_ExpenseExampleYear10	2,140
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	164
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	556
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	974
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,140
1 YEAR	rr_AverageAnnualReturnYear01	3.57%
5 YEARS	rr_AverageAnnualReturnYear05	1.93%
10 YEARS	rr_AverageAnnualReturnYear10	3.13%
AB MUNICIPAL INCOME FUND II | AB Pennsylvania Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.09%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.01%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.49%	[5]
AB MUNICIPAL INCOME FUND II | AB Pennsylvania Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.45%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.24%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.51%	[5]
AB MUNICIPAL INCOME FUND II | AB Pennsylvania Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ----- .85% 1.60% 1.60%

[5] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[6] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

XML

AB MUNICIPAL INCOME FUND II | AB Virginia Portfolio

AB VIRGINIA PORTFOLIO

INVESTMENT OBJECTIVE:

The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and Commonwealth of Virginia personal income tax that is available without assuming what the Adviser considers to be undue risk.

FEES AND EXPENSES OF THE PORTFOLIO:

This table describes the fees and expenses that you may pay if you buy and hold shares of the Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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) <!-- $$/page= -->

Shareholder Fees - AB MUNICIPAL INCOME FUND II - AB Virginia Portfolio	CLASS A SHARES	CLASS B SHARES		CLASS C SHARES		ADVISOR CLASS SHARES
Shareholder Fees Column [Text]		(NOT CURRENTLY OFFERED TO NEW INVESTORS)
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%	none		none		none
Maximum Deferred Sales Charge (Load) (as a percentage of offering price or redemption proceeds, whichever is lower)	none	3.00%	[1]	1.00%	[2]	none
Exchange Fee	none	none		none		none

ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)

Annual Portfolio Operating Expenses - AB MUNICIPAL INCOME FUND II - AB Virginia Portfolio		CLASS A	CLASS B	CLASS C	ADVISOR CLASS
Management Fees		0.45%	0.45%	0.45%	0.45%
Distribution and/or Service (12b-1) Fees		0.25%	1.00%	1.00%	none
Other Expenses: Transfer Agent		0.04%	0.08%	0.04%	0.04%
Other Expenses: Interest Expense		0.01%	0.01%	0.01%	0.01%
Other Expenses		0.14%	0.14%	0.15%	0.14%
Total Other Expenses		0.19%	0.23%	0.20%	0.19%
Total Annual Portfolio Operating Expenses	[1]	0.89%	1.68%	1.65%	0.64%
Fee Waiver and/or Expense Reimbursement	[2]	(0.08%)	(0.12%)	(0.09%)	(0.08%)
Total Annual Portfolio Operating Expenses	[3],[4]	0.81%	1.56%	1.56%	0.56%

EXAMPLES

The Examples are intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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 MUNICIPAL INCOME FUND II - AB Virginia Portfolio - USD ($)	CLASS A	CLASS B	CLASS C	ADVISOR CLASS
After 1 Year	$ 380	$ 459	$ 259	$ 57
After 3 Years	568	618	512	197
After 5 Years	771	901	888	349
After 10 Years	$ 1,356	$ 1,573	$ 1,947	$ 791

For the shares 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 MUNICIPAL INCOME FUND II - AB Virginia Portfolio - USD ($)	CLASS B	CLASS C
After 1 Year	$ 159	$ 159
After 3 Years	518	512
After 5 Years	901	888
After 10 Years	$ 1,573	$ 1,947

PORTFOLIO TURNOVER

The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 18% of the average value of its portfolio.

PRINCIPAL STRATEGIES:

The Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Virginia or municipal securities with interest that is otherwise exempt from Virginia state income tax.

The Portfolio may also invest in:

• forward commitments;

• zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and

• derivatives, such as options, futures contracts, forwards and swaps.

PRINCIPAL RISKS:

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

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

• MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Virginia municipal securities may be vulnerable to events adversely affecting its economy. Virginia has a highly diversified economy, with services, agriculture and tourism as major components. The U.S. Government, both military and civilian, plays a large role in its economy. The state benefits from increases in U.S. Government spending but is vulnerable to spending decreases. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.
  
  Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities.
  
  The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility.

• TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

• INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations.

• DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

• INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

• LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

• DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments.

• MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.

BAR CHART AND PERFORMANCE INFORMATION:

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

• how the Portfolio's performance changed from year to year over ten years; and

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

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

The Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.30%.

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

BEST QUARTER WAS UP 5.98%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.03%, 2ND QUARTER, 2013.

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

Average Annual Total Returns - AB MUNICIPAL INCOME FUND II - AB Virginia Portfolio		1 YEAR	5 YEARS	10 YEARS	INCEPTION DATE
CLASS A	[1]	1.84%	1.91%	3.86%
CLASS A | Return After Taxes on Distributions	[1]	1.80%	1.86%	3.79%
CLASS A | Return After Taxes on Distributions and Sale of Portfolio Shares	[1]	2.30%	2.12%	3.75%
CLASS B		1.32%	1.82%	3.75%
CLASS C		3.33%	1.83%	3.46%
ADVISOR CLASS	[2]	5.37%	2.82%	4.45%	Jul. 25, 2016
Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)		5.45%	3.02%	4.46%

[1] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

[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] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ADVISOR CLASS ----- .80% 1.55% 1.55% .55%

[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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[2] Inception date for Advisor Class shares: 7/25/2016. Performance information for period prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
AB MUNICIPAL INCOME FUND II | AB Virginia Portfolio
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	AB VIRGINIA PORTFOLIO
Objective [Heading]	rr_ObjectiveHeading	INVESTMENT OBJECTIVE:
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of the Portfolio is to earn the highest level of current income exempt from both federal income tax and Commonwealth of Virginia personal income tax that is available without assuming what the Adviser considers to be undue risk.
Expense [Heading]	rr_ExpenseHeading	FEES AND EXPENSES OF THE PORTFOLIO:
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 Portfolio. 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 Portfolios--Sales Charge Reduction Programs for Class A Shares on page 71 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 156 of the Portfolio'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) <!-- $$/page= -->
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL PORTFOLIO OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 28, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	PORTFOLIO TURNOVER
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Portfolio pays transaction costs, such as commissions, when it buys or sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Portfolio shares are held in a taxable account. These transaction costs, which are not reflected in the Annual Portfolio Operating Expenses or in the Examples, affect the Portfolio's performance. During the most recent fiscal year, the Portfolio's portfolio turnover rate was 18% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	18.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third 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 Portfolio with the cost of investing in other mutual funds. The Examples assume that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The Examples also assume that your investment has a 5% return each year, that the Portfolio's operating expenses stay the same and that any fee waiver and/or expense limitation 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, No Redemption, By Year, Caption [Text]	rr_ExpenseExampleNoRedemptionByYearCaption	For the shares 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 Portfolio pursues its objective by investing principally in high-yielding, predominantly investment grade municipal securities. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities that pay interest that is exempt from federal income tax. These securities may pay interest that is subject to the federal alternative minimum tax ("AMT") for certain taxpayers. As a matter of fundamental policy, the Portfolio invests, under normal circumstances, at least 80% of its net assets in municipal securities of Virginia or municipal securities with interest that is otherwise exempt from Virginia state income tax. The Portfolio may also invest in: forward commitments; zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities; and derivatives, such as options, futures contracts, forwards and swaps.
Risk [Heading]	rr_RiskHeading	PRINCIPAL RISKS:
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	MARKET RISK: The value of the Portfolio's assets will fluctuate as the bond market fluctuates. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events that affect large portions of the market. CREDIT RISK: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security. Investments in fixed-income securities with lower ratings tend to have a higher probability that an issuer will default or fail to meet its payment obligations. MUNICIPAL MARKET RISK: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, uncertainties related to the tax status of municipal securities, or the rights of investors in these securities. The Portfolio's investments in Virginia municipal securities may be vulnerable to events adversely affecting its economy. Virginia has a highly diversified economy, with services, agriculture and tourism as major components. The U.S. Government, both military and civilian, plays a large role in its economy. The state benefits from increases in U.S. Government spending but is vulnerable to spending decreases. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities. Recent tax law changes could have a material impact on the value of municipal securities. In addition, Congress has previously considered making changes to the municipal securities provisions of the Internal Revenue Code that could change the U.S. federal income tax treatment of certain types of municipal securities. The Portfolio may invest in the municipal securities of Puerto Rico and other U.S. territories and their governmental agencies and municipalities, which are exempt from federal, state, and, where applicable, local income taxes. These municipal securities may have more risks than those of other U.S. issuers of municipal securities. Like many U.S. states and municipalities, Puerto Rico experienced a significant downturn during the recent recession. Puerto Rico's downturn was particularly severe, and Puerto Rico continues to face a very challenging economic and fiscal environment. If the general economic situation in Puerto Rico continues to persist or worsens, the volatility and credit quality of Puerto Rican municipal securities could continue to be adversely affected, and the market for such securities may experience continued volatility. TAX RISK: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in federal tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's net asset value, or NAV, could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield. INTEREST RATE RISK: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. DURATION RISK: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise. INFLATION RISK: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities. LIQUIDITY RISK: Liquidity risk occurs when certain investments become difficult to purchase or sell. Difficulty in selling less liquid securities may result in sales at disadvantageous prices affecting the value of your investment in the Portfolio. Causes of liquidity risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Over recent years liquidity risk has also increased because the capacity of dealers in the secondary market for fixed-income securities to make markets in these securities has decreased, even as the overall bond market has grown significantly, due to, among other things, structural changes, additional regulatory requirements and capital and risk restraints that have led to reduced inventories. Liquidity risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more liquidity risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets. DERIVATIVES RISK: Derivatives may be illiquid, difficult to price, and leveraged so that small changes may produce disproportionate losses for the Portfolio, and may be subject to counterparty risk to a greater degree than more traditional investments. MANAGEMENT RISK: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, 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 Portfolio.
Risk Lose Money [Text]	rr_RiskLoseMoney	As with all investments, you may lose money by investing in the Portfolio.
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 Portfolio by showing: how the Portfolio's performance changed from year to year over ten years; and how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index. You may obtain updated performance information on the Portfolio's website at www.abfunds.com (click on "Investments--Mutual Funds"). The Portfolio'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 Portfolio's performance changed from year to year over ten years; and</li></ul><ul type="square"><li>how the Portfolio'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 Portfolio'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 Portfolio's Class A shares and do not reflect sales loads. If sales loads were reflected, returns would be less than those shown. Through June 30, 2018, the year-to-date unannualized return for Class A shares was -0.30%.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The annual returns in the bar chart are for the Portfolio'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 Portfolio's: BEST QUARTER WAS UP 5.98%, 3RD QUARTER, 2009; AND WORST QUARTER WAS DOWN -4.03%, 2ND QUARTER, 2013.
Performance Table Heading	rr_PerformanceTableHeading	PERFORMANCE TABLE<br/>AVERAGE ANNUAL TOTAL RETURNS<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 Portfolio 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 MUNICIPAL INCOME FUND II | AB Virginia Portfolio | CLASS A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.14%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.89%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.81%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 380
After 3 Years	rr_ExpenseExampleYear03	568
After 5 Years	rr_ExpenseExampleYear05	771
After 10 Years	rr_ExpenseExampleYear10	$ 1,356
2008	rr_AnnualReturn2008	(4.83%)
2009	rr_AnnualReturn2009	14.54%
2010	rr_AnnualReturn2010	2.70%
2011	rr_AnnualReturn2011	10.72%
2012	rr_AnnualReturn2012	7.15%
2013	rr_AnnualReturn2013	(4.90%)
2014	rr_AnnualReturn2014	9.39%
2015	rr_AnnualReturn2015	3.12%
2016	rr_AnnualReturn2016	0.65%
2017	rr_AnnualReturn2017	5.00%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Jun. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(0.30%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	BEST QUARTER
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.98%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	WORST QUARTER
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2013
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.03%)
1 YEAR	rr_AverageAnnualReturnYear01	1.84%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	1.91%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.86%	[5]
AB MUNICIPAL INCOME FUND II | AB Virginia 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	3.00%	[6]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.08%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.14%
Total Other Expenses	rr_OtherExpensesOverAssets	0.23%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.68%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.12%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.56%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 459
After 3 Years	rr_ExpenseExampleYear03	618
After 5 Years	rr_ExpenseExampleYear05	901
After 10 Years	rr_ExpenseExampleYear10	1,573
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	159
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	518
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	901
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,573
1 YEAR	rr_AverageAnnualReturnYear01	1.32%
5 YEARS	rr_AverageAnnualReturnYear05	1.82%
10 YEARS	rr_AverageAnnualReturnYear10	3.75%
AB MUNICIPAL INCOME FUND II | AB Virginia 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%	[7]
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.15%
Total Other Expenses	rr_OtherExpensesOverAssets	0.20%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	1.65%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.09%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	1.56%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 259
After 3 Years	rr_ExpenseExampleYear03	512
After 5 Years	rr_ExpenseExampleYear05	888
After 10 Years	rr_ExpenseExampleYear10	1,947
After 1 Year	rr_ExpenseExampleNoRedemptionYear01	159
After 3 Years	rr_ExpenseExampleNoRedemptionYear03	512
After 5 Years	rr_ExpenseExampleNoRedemptionYear05	888
After 10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,947
1 YEAR	rr_AverageAnnualReturnYear01	3.33%
5 YEARS	rr_AverageAnnualReturnYear05	1.83%
10 YEARS	rr_AverageAnnualReturnYear10	3.46%
AB MUNICIPAL INCOME FUND II | AB Virginia 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	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses: Transfer Agent	rr_Component1OtherExpensesOverAssets	0.04%
Other Expenses: Interest Expense	rr_Component2OtherExpensesOverAssets	0.01%
Other Expenses	rr_Component3OtherExpensesOverAssets	0.14%
Total Other Expenses	rr_OtherExpensesOverAssets	0.19%
Total Annual Portfolio Operating Expenses	rr_ExpensesOverAssets	0.64%	[1]
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2]
Total Annual Portfolio Operating Expenses	rr_NetExpensesOverAssets	0.56%	[3],[4]
After 1 Year	rr_ExpenseExampleYear01	$ 57
After 3 Years	rr_ExpenseExampleYear03	197
After 5 Years	rr_ExpenseExampleYear05	349
After 10 Years	rr_ExpenseExampleYear10	$ 791
1 YEAR	rr_AverageAnnualReturnYear01	5.37%	[8]
5 YEARS	rr_AverageAnnualReturnYear05	2.82%	[8]
10 YEARS	rr_AverageAnnualReturnYear10	4.45%	[8]
INCEPTION DATE	rr_AverageAnnualReturnInceptionDate	Jul. 25, 2016	[8]
AB MUNICIPAL INCOME FUND II | AB Virginia Portfolio | Return After Taxes on Distributions | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	1.80%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	1.86%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.79%	[5]
AB MUNICIPAL INCOME FUND II | AB Virginia Portfolio | Return After Taxes on Distributions and Sale of Portfolio Shares | CLASS A
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	2.30%	[5]
5 YEARS	rr_AverageAnnualReturnYear05	2.12%	[5]
10 YEARS	rr_AverageAnnualReturnYear10	3.75%	[5]
AB MUNICIPAL INCOME FUND II | AB Virginia Portfolio | Bloomberg Barclays Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 YEAR	rr_AverageAnnualReturnYear01	5.45%
5 YEARS	rr_AverageAnnualReturnYear05	3.02%
10 YEARS	rr_AverageAnnualReturnYear10	4.46%

[1] Before Waiver

[2] The fee waiver and/or expense reimbursement agreement will remain in effect until September 28, 2019 and will be automatically extended for one-year terms thereafter unless terminated by the Adviser upon 60 days' notice to the Portfolio prior to that date.

[3] After Fee Waiver and/or Expense Reimbursement

[4] If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows: CLASS A CLASS B CLASS C ADVISOR CLASS ----- .80% 1.55% 1.55% .55%

[5] 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 Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

[6] Class B shares automatically convert to Class A shares after six years. The contingent deferred sales charge, or CDSC, decreases over time. For Class B shares, the CDSC decreases 1.00% annually to 0% after the third year.

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

[8] Inception date for Advisor Class shares: 7/25/2016. Performance information for period prior to the inception of Advisor Class shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Advisor Class shares.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	AB MUNICIPAL INCOME FUND, INC.
Prospectus Date	rr_ProspectusDate	Sep. 28, 2018
Document Creation Date	dei_DocumentCreationDate	Sep. 28, 2018