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BNY Mellon Opportunistic Municipal Securities Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Fund Summary
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund seeks to maximize current income exempt from federal income tax to the extent consistent with the preservation of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or shares of other funds in the BNY Mellon Family of Funds that are subject to a sales charge. More information about sales charges, including these and other discounts and waivers, is available from your financial professional and in the Shareholder Guide section beginning on page 11 of the prospectus, in the Appendix on page A-1 of the prospectus and in the How to Buy Shares section and the Additional Information About How to Buy Shares section beginning on page II-1 and page III-1, respectively, of the fund's Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 21.69% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 21.69%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or shares of other funds in the BNY Mellon Family of Funds that are subject to a sales charge.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
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. The Example also assumes that your investment has a 5% return each year and that the fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

To pursue its goal, the fund normally invests at least 80% of its net assets, plus any borrowings for investment purposes, in municipal bonds that provide income exempt from federal personal income tax. Typically, the fund invests substantially all of its assets in such municipal bonds. Municipal bonds are debt securities or other obligations issued by states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities, or multistate agencies and authorities, and certain other specified securities.

The fund invests at least 70% of its net assets in municipal bonds rated, at the time of purchase, investment grade (i.e., Baa/BBB or higher) or the unrated equivalent as determined by Insight North America LLC, the fund's sub-adviser. For additional yield, the fund may invest up to 30% of its net assets in municipal bonds rated, at the time of purchase, below investment grade ("high yield" or "junk" bonds) or the unrated equivalent as determined by the fund's sub-adviser. The dollar-weighted average maturity of the fund's portfolio normally exceeds ten years, but the fund may invest without regard to maturity or duration. A bond's maturity is the length of time until the principal must be fully repaid with interest. Dollar-weighted average maturity is an average of the stated maturities of the bonds held by the fund, based on their dollar-weighted proportions in the fund. Duration is an indication of an investment's "interest rate risk," or how sensitive a bond or the fund's portfolio may be to changes in interest rates.

The fund's sub-adviser focuses on identifying undervalued sectors and securities. To select municipal bonds for the fund, the sub-adviser uses fundamental credit analysis to estimate the relative value and attractiveness of various sectors and securities and actively trades among various sectors and securities based on their apparent relative values. The fund seeks to invest in several different sectors, and does not seek to overweight any particular sector but may do so depending on each sector's relative value at a given time.

A rigorous sell discipline is employed to continuously evaluate all fund holdings. Current holdings may become sell candidates if creditworthiness is deteriorating, if bonds with better risk and return characteristics become available, or if the holding no longer meets the sub-adviser's strategic or structural objectives.

Although the fund seeks to provide income exempt from federal income tax, interest from some of the fund's holdings may be subject to the federal alternative minimum tax.
Risk [Heading] rr_RiskHeading Principal Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the performance of the fund's Class A shares from year to year. Sales charges, if any, are not reflected in the bar chart and, if those charges were included, returns would have been less than those shown. The table compares the average annual total returns of the fund's shares to those of a broad measure of market performance. The fund's past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. More recent performance information may be available at www.im.bnymellon.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.im.bnymellon.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund's past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Year-by-Year Total Returns as of 12/31 each year (%) Class A
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges, if any, are not reflected in the bar chart and, if those charges were included, returns would have been less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

During the periods
shown in the chart:

Best Quarter
Q1, 2014: 4.04%

Worst Quarter
Q1, 2022: -6.12%

The year-to-date total return of the fund's Class A shares as of June 30, 2023 was 3.02%.
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2023
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.02%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2014
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 4.04%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (6.12%)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes reflects no deductions for fees, expenses or taxes
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest 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 the investor's tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through U.S. 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 performance is shown only for Class A shares. After-tax performance of the fund's other share classes will vary.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher Returns after taxes on distributions and sale of fund shares may be higher than returns before taxes or returns after taxes on distributions due to an assumed tax benefit from losses on a sale of the fund's shares at the end of the period.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax performance is shown only for Class A shares. After-tax performance of the fund's other share classes will vary. After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor's tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through U.S. tax-deferred arrangements such as 401(k) plans or individual retirement accounts. Returns after taxes on distributions and sale of fund shares may be higher than returns before taxes or returns after taxes on distributions due to an assumed tax benefit from losses on a sale of the fund's shares at the end of the period.

For the fund's Class I and Class Y shares, periods prior to the inception date reflect the performance of the fund's Class A shares, without reflecting any applicable sales charges for Class A shares. Such performance figures have not been adjusted to reflect applicable class fees and expenses. Each share class is invested in the same portfolio of securities, and the annual returns would have differed only to the extent that the classes have different expenses.

Average Annual Return, Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (as of 12/31/22)
BNY Mellon Opportunistic Municipal Securities Fund | Risk Not Insured [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock An investment in the fund is not a bank deposit. It is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency.
BNY Mellon Opportunistic Municipal Securities Fund | Risk Lose Money [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock The fund's share price fluctuates, sometimes dramatically, which means you could lose money.
BNY Mellon Opportunistic Municipal Securities Fund | Municipal securities risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock ● Municipal securities risk . The amount of public information available about municipal securities is generally less than that for corporate equities or bonds. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the fund's investments in municipal securities. Other factors include the general conditions of the municipal securities market, the size of the particular offering, the maturity of the obligation and the rating of the issue. Changes in economic, business or political conditions relating to a particular municipal project, municipality, or state, territory or possession of the United States in which the fund invests may have an impact on the fund's share price. Any credit impairment could adversely impact the value of their bonds, which could negatively impact the performance of the fund.
BNY Mellon Opportunistic Municipal Securities Fund | Interest rate risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock ● Interest rate risk. Prices of bonds and other fixed rate fixed-income securities tend to move inversely with changes in interest rates. Typically, a rise in rates will adversely affect fixed-income securities and, accordingly, will cause the value of the fund's investments in these securities to decline. Interest rates in the United States have been rising and may continue to increase in the near future. A wide variety of market factors can cause interest rates to rise, including central bank monetary policy, rising inflation and changes in general economic conditions. During periods of very low interest rates, which occur from time to time due to market forces or actions of governments and/or their central banks, including the Board of Governors of the Federal Reserve System in the U.S., the fund may be subject to a greater risk of principal decline from rising interest rates. When interest rates fall, the fund's investments in new securities may be at lower yields and may reduce the fund's income. Changing interest rates may have unpredictable effects on markets, may result in heightened market volatility and may detract from fund performance. The magnitude of these fluctuations in the market price of fixed-income securities is generally greater for securities with longer effective maturities and durations because such instruments do not mature, reset interest rates or become callable for longer periods of time. Unlike investment grade bonds, however, the prices of high yield ("junk") bonds may fluctuate unpredictably and not necessarily inversely with changes in interest rates.
BNY Mellon Opportunistic Municipal Securities Fund | Credit risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock ● Credit risk. Failure of an issuer of a security to make timely interest or principal payments when due, or a decline or perception of a decline in the credit quality of the security, can cause the security's price to fall. The lower a security's credit rating, the greater the chance that the issuer of the security will default or fail to meet its payment obligations.
BNY Mellon Opportunistic Municipal Securities Fund | High yield securities risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock ● High yield securities risk. High yield ("junk") securities involve greater credit risk, including the risk of default, than investment grade securities, and are considered predominantly speculative with respect to the issuer's ability to make principal and interest payments. These securities are especially sensitive to adverse changes in general economic conditions, to changes in the financial condition of their issuers and to price fluctuation in response to changes in interest rates. During periods of economic downturn or rising interest rates, issuers of below investment grade securities may experience financial stress that could adversely affect their ability to make payments of principal and interest and increase the possibility of default.
BNY Mellon Opportunistic Municipal Securities Fund | Liquidity risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock ● Liquidity risk. When there is little or no active trading market for specific types of securities, it can become more difficult to sell the securities in a timely manner at or near their perceived value. In such a market, the value of such securities and the fund's share price may fall dramatically. The secondary market for certain municipal bonds tends to be less well developed or liquid than many other securities markets, which may adversely affect the fund's ability to sell such municipal bonds at attractive prices. Investments that are illiquid or that trade in lower volumes may be more difficult to value. The market for below investment grade securities may be less liquid and therefore these securities may be harder to value or sell at an acceptable price, especially during times of market volatility or decline.
BNY Mellon Opportunistic Municipal Securities Fund | Market risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock ● Market risk. The value of the securities in which the fund invests may be affected by political, regulatory, economic and social developments, and developments that impact specific economic sectors, industries or segments of the market.  In addition, turbulence in financial markets and reduced liquidity in equity, credit and/or fixed-income markets may negatively affect many issuers, which could adversely affect the fund.  Global economies and financial markets are becoming increasingly interconnected, and conditions and events in one country, region or financial market may adversely impact issuers in a different country, region or financial market.  These risks may be magnified if certain events or developments adversely interrupt the global supply chain; in these and other circumstances, such risks might affect companies world-wide.
BNY Mellon Opportunistic Municipal Securities Fund | Management risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock ● Management risk. The investment process used by the fund's sub-adviser could fail to achieve the fund's investment goal and cause your fund investment to lose value.
BNY Mellon Opportunistic Municipal Securities Fund | Bloomberg U.S. Municipal Bond Index reflects no deductions for fees, expenses or taxes  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (8.53%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.25%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 2.13%
BNY Mellon Opportunistic Municipal Securities 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_MaximumDeferredSalesChargeOverOfferingPrice none [1]
Management fees rr_ManagementFeesOverAssets 0.35%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Shareholder services fees rr_Component1OtherExpensesOverAssets 0.25%
Miscellaneous other expenses rr_Component2OtherExpensesOverAssets 0.12%
Total other expenses rr_OtherExpensesOverAssets 0.37%
Total annual fund operating expenses rr_ExpensesOverAssets 0.72%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock Class A shares bought without an initial sales charge as part of an investment of $250,000 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 $ 519
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 669
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 832
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,303
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 519
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 669
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 832
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,303
Annual Return 2013 rr_AnnualReturn2013 (3.87%)
Annual Return 2014 rr_AnnualReturn2014 11.25%
Annual Return 2015 rr_AnnualReturn2015 3.59%
Annual Return 2016 rr_AnnualReturn2016 (0.59%)
Annual Return 2017 rr_AnnualReturn2017 5.74%
Annual Return 2018 rr_AnnualReturn2018 0.53%
Annual Return 2019 rr_AnnualReturn2019 8.02%
Annual Return 2020 rr_AnnualReturn2020 5.01%
Annual Return 2021 rr_AnnualReturn2021 1.89%
Annual Return 2022 rr_AnnualReturn2022 (9.87%)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (13.90%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 none
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.53%
BNY Mellon Opportunistic Municipal Securities Fund | Class A | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (13.96%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 (0.05%)
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.51%
BNY Mellon Opportunistic Municipal Securities Fund | Class A | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (7.35%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.62%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.85%
BNY Mellon Opportunistic Municipal Securities 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_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management fees rr_ManagementFeesOverAssets 0.35%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.75%
Shareholder services fees rr_Component1OtherExpensesOverAssets 0.25%
Miscellaneous other expenses rr_Component2OtherExpensesOverAssets 0.16%
Total other expenses rr_OtherExpensesOverAssets 0.41%
Total annual fund operating expenses rr_ExpensesOverAssets 1.51%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 253
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 476
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 823
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,801
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 153
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 476
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 823
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,801
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (11.50%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.13%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.21%
BNY Mellon Opportunistic Municipal Securities Fund | Class I  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management fees rr_ManagementFeesOverAssets 0.35%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Shareholder services fees rr_Component1OtherExpensesOverAssets none
Miscellaneous other expenses rr_Component2OtherExpensesOverAssets 0.14%
Total other expenses rr_OtherExpensesOverAssets 0.14%
Total annual fund operating expenses rr_ExpensesOverAssets 0.49%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 49
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 156
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 273
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 615
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 49
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 156
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 273
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 615
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (9.72%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.17%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 2.16%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 31, 2016
BNY Mellon Opportunistic Municipal Securities 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_MaximumDeferredSalesChargeOverOfferingPrice none
Management fees rr_ManagementFeesOverAssets 0.35%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Shareholder services fees rr_Component1OtherExpensesOverAssets none
Miscellaneous other expenses rr_Component2OtherExpensesOverAssets 0.13%
Total other expenses rr_OtherExpensesOverAssets 0.13%
Total annual fund operating expenses rr_ExpensesOverAssets 0.48%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 48
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 153
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 268
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 603
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 48
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 153
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 268
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 603
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (9.64%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.17%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 2.12%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 31, 2016
BNY Mellon Opportunistic Municipal Securities 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_MaximumDeferredSalesChargeOverOfferingPrice none
Management fees rr_ManagementFeesOverAssets 0.35%
Distribution (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Shareholder services fees rr_Component1OtherExpensesOverAssets 0.20%
Miscellaneous other expenses rr_Component2OtherExpensesOverAssets 0.13%
Total other expenses rr_OtherExpensesOverAssets 0.33%
Total annual fund operating expenses rr_ExpensesOverAssets 0.68%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 68
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 217
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 378
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 846
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 68
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 217
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 378
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 846
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (9.83%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.98%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 2.06%
[1] Class A shares bought without an initial sales charge as part of an investment of $250,000 or more may be charged a deferred sales charge of 1.00% if redeemed within one year.