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Fund Summary

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The fund seeks as high a level of income exempt from federal and Massachusetts state income taxes as is consistent with the preservation of capital.

Expense Narrative [Text Block]

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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.

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover, Rate

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48.39%

Expense Example Narrative [Text Block]

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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 hold or 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. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Strategy Narrative [Text Block]

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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 and Massachusetts state personal income taxes. These municipal bonds include those issued by the Commonwealth of Massachusetts as well as those issued by territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities, or multistate agencies and authorities.

The fund's investments in municipal and taxable bonds must be rated investment grade (i.e., Baa/BBB or higher) at the time of purchase or, if unrated, deemed of comparable quality by the fund's sub-adviser, Insight North America LLC (INA), an affiliate of BNY Mellon Investment Adviser, Inc. (BNYIA). Generally, the fund's average effective portfolio

maturity will be between three and ten years and the average effective duration of the fund's portfolio will not exceed eight years. Because of events affecting the bond markets and interest rate changes, the maturity and duration of the portfolio might not meet the foregoing targets at all times. The fund may invest in individual municipal and taxable bonds of any maturity or duration. A bond's maturity is the length of time until the principal must be fully repaid with interest. Average effective portfolio maturity is an average of the maturities of bonds held by the fund directly and the bonds underlying derivative instruments entered into by the fund, if any, adjusted to reflect provisions or market conditions that may cause a bond's principal to be repaid earlier than at its stated maturity. 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.

Although the fund seeks to provide income exempt from federal and Massachusetts state income taxes, income from some of the fund's holdings may be subject to the federal alternative minimum tax.

The fund's sub-adviser focuses on identifying undervalued sectors and securities. To select municipal bonds for the fund, the fund's sub-adviser uses fundamental credit analysis to estimate the relative value and attractiveness of various sectors and securities and to exploit pricing inefficiencies in the municipal bond market. The fund's sub-adviser actively trades among various sectors and securities based on their apparent relative values. The fund seeks to invest in several different sectors and may overweight a particular sector depending on each sector's relative value at a given time.

The fund typically sells a security when the fund's sub-adviser believes that there has been a negative change in the credit quality of the issuer or has identified a more attractive opportunity or when the sub-adviser seeks to manage the fund's duration or tax position or to provide liquidity to meet shareholder redemptions.

Performance Narrative [Text Block]

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The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows the performance of the fund's Class M shares from year to year. The table compares the average annual total returns of the fund's Class M shares and Investor shares to those of the Bloomberg U.S. Municipal Bond Index and S&P Municipal Bond Index, broad measures of market performance, and the Bloomberg Muni 3-15 Years Blend Index and S&P Municipal Bond Investment Grade Intermediate Index, indices reflecting the market segments in which the fund invests.

Performance Past Does Not Indicate Future [Text]

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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 Closing [Text Block]

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During the periods shown in the chart:
Best Quarter
2023, Q4: 6.37
Worst Quarter
2022, Q1: (5.58)

The year-to-date total return of the fund's Class M shares as of September 30, 2025 was 3.11%.

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal tax rates, and do not reflect the impact of state and local taxes.

Performance Table Explanation after Tax Higher

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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.

Average Annual Return, Caption [Optional Text]

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Average Annual Total Returns as of 12/31/24

Risk/Return:

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Risk [Text Block]

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The fund's share price fluctuates, sometimes dramatically, which means you could lose money.

Risk/Return:

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Risk [Text Block]

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· Municipal securities risk: Municipal securities are subject to interest rate, credit, liquidity, valuation, market and political risks. The amount of public information available about municipal securities is generally less than that for corporate equities or bonds. Special factors, such as legislative and regulatory changes, executive orders, voter initiatives, and state and local economic and business developments, may adversely affect the 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 municipal bonds, which could negatively impact the performance of the fund. In addition, income from municipal securities held by the fund could be declared taxable because of, among other things, unfavorable changes in tax laws, adverse interpretations by the Internal Revenue Service or state tax authorities, or noncompliant conduct of an issuer or other obligated party. Loss of tax-exempt status for municipal securities held by the fund may cause interest received and distributed to shareholders by the fund to be taxable and may result in a significant decline in the values of such municipal securities.

Risk/Return:

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Risk [Text Block]

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· Prepayment risk: Some securities give the issuer the option to prepay or call the securities before their maturity date, which may reduce the market value of the security and the anticipated yield-to-maturity. Issuers often exercise this right when interest rates fall. If an issuer "calls" its securities during a time of declining interest rates, the fund might have to reinvest the proceeds in an investment offering a lower yield, and therefore might not benefit from any increase in value as a result of declining interest rates. During periods of market illiquidity or rising interest rates, prices of "callable" issues are subject to increased price fluctuation.

Risk/Return:

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Risk [Text Block]

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· 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 buy or sell such municipal bonds at attractive prices. Investments that are illiquid or that trade in lower volumes may be more difficult to value.

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Risk [Text Block]

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· Valuation risk: The price that the fund could receive upon the sale (or other disposition) of an investment may differ from the fund's valuation of the investment, particularly for investments that trade in lower volumes, investments that are valued using a fair valuation methodology or a price provided by an independent pricing service, or during market turmoil or volatility. As a result, the price received upon the sale of an investment may be less than the value ascribed by the fund, and the fund could realize a greater than expected loss or lesser than expected gain upon the sale of the investment.

Risk/Return:

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Risk [Text Block]

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· 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. Local, regional or global events such as war, military conflicts, acts of terrorism, natural disasters, the spread of infectious illness or other public health issues, recessions, elevated levels of government debt, changes in trade regulation or economic sanctions, internal unrest and discord, or other events could have a significant impact on the fund and its investments.

Risk/Return:

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