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Class A, C, I, Y, Z Prospectus | Dreyfus High Yield Municipal Bond Fund  
Risk/Return: rr_RiskReturnAbstract  
Supplement [Text Block] ck0000878092_SupplementTextBlock

May 1, 2017


DREYFUS MUNICIPAL FUNDS, INC.


-          DREYFUS HIGH YIELD MUNICIPAL BOND FUND


(Class A, C, I, Y and Z Shares)


Supplement to Summary and Statutory Prospectuses


Dated December 30, 2016
Risk/Return [Heading] rr_RiskReturnHeading Dreyfus High Yield Municipal Bond Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

The following information supersedes and replaces any contrary information contained in “Fees and Expenses” in the fund’s summary prospectus and “Fund Summary - Fees and Expenses” in the fund’s statutory prospectus:
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination Dec. 31, 2017
Expenses Restated to Reflect Current [Text] rr_ExpensesRestatedToReflectCurrent Restated to reflect current management fee.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The Example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.  The Example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods.  The Example also assumes that your investment has a 5% return each year and that the fund's operating expenses remain the same.  The one-year example and the first year of the three-, five- and ten-year examples are based on net operating expenses, which reflect the expense limitation by The Dreyfus Corporation.  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 You would pay the following expenses if you did not redeem your shares:
Class A, C, I, Y, Z Prospectus | Dreyfus High Yield Municipal Bond Fund | Class A  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.50%
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none [1]
Redemption Fee (as a percentage of Amount Redeemed) rr_RedemptionFeeOverRedemption (2.00%)
Management fees rr_ManagementFeesOverAssets 0.50% [2]
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.43%
Total annual fund operating expenses rr_ExpensesOverAssets 0.93%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.06%) [3]
Total annual fund operating expenses (after fee waiver and/or expense reimbursement) rr_NetExpensesOverAssets 0.87%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock Class A shares bought without an initial sales charge as part of an investment of $1 million or more may be charged a deferred sales charge of 1.00% if redeemed within one year.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 535
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 727
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 936
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,536
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 535
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 727
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 936
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,536
Class A, C, I, Y, Z Prospectus | Dreyfus High Yield Municipal Bond Fund | Class C  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther 1.00%
Redemption Fee (as a percentage of Amount Redeemed) rr_RedemptionFeeOverRedemption (2.00%)
Management fees rr_ManagementFeesOverAssets 0.50% [2]
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.75%
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.45%
Total annual fund operating expenses rr_ExpensesOverAssets 1.70%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.08%) [3]
Total annual fund operating expenses (after fee waiver and/or expense reimbursement) rr_NetExpensesOverAssets 1.62%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 265
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 528
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 915
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,002
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 165
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 528
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 915
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,002
Class A, C, I, Y, Z Prospectus | Dreyfus High Yield Municipal Bond Fund | Class I Shares  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none
Redemption Fee (as a percentage of Amount Redeemed) rr_RedemptionFeeOverRedemption (2.00%)
Management fees rr_ManagementFeesOverAssets 0.50% [2]
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.20%
Total annual fund operating expenses rr_ExpensesOverAssets 0.70%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.08%) [3]
Total annual fund operating expenses (after fee waiver and/or expense reimbursement) rr_NetExpensesOverAssets 0.62%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 63
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 216
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 382
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 863
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 63
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 216
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 382
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 863
Class A, C, I, Y, Z Prospectus | Dreyfus High Yield Municipal Bond Fund | Class Y  
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 lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none
Redemption Fee (as a percentage of Amount Redeemed) rr_RedemptionFeeOverRedemption (2.00%)
Management fees rr_ManagementFeesOverAssets 0.50% [2]
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.16%
Total annual fund operating expenses rr_ExpensesOverAssets 0.66%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [3]
Total annual fund operating expenses (after fee waiver and/or expense reimbursement) rr_NetExpensesOverAssets 0.62%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 63
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 207
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 364
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 819
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 63
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 207
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 364
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 819
Class A, C, I, Y, Z Prospectus | Dreyfus High Yield Municipal Bond Fund | Class Z  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none
Redemption Fee (as a percentage of Amount Redeemed) rr_RedemptionFeeOverRedemption (2.00%)
Management fees rr_ManagementFeesOverAssets 0.50% [2]
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.18%
Total annual fund operating expenses rr_ExpensesOverAssets 0.83%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.06%) [3]
Total annual fund operating expenses (after fee waiver and/or expense reimbursement) rr_NetExpensesOverAssets 0.77%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 79
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 259
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 455
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,020
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 79
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 259
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 455
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,020
[1] Class A shares bought without an initial sales charge as part of an investment of $1 million or more may be charged a deferred sales charge of 1.00% if redeemed within one year.
[2] Restated to reflect current management fee.
[3] The fund's investment adviser, The Dreyfus Corporation, has contractually agreed, until December 31, 2017, to waive receipt of its fees and/or assume the expenses of the fund so that the total annual fund operating expenses of Class A, C, I, Y and Z shares (excluding Rule 12b-1 fees, shareholder services fees, taxes, interest, brokerage commissions, commitment fees on borrowings and extraordinary expenses) do not exceed .62%. On or after December 31, 2017, The Dreyfus Corporation may terminate this expense limitation at any time.