v3.25.2
Shareholder Report, Holdings (Details)
May 31, 2025
C000193017 [Member] | CCC and below [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.50%
C000193017 [Member] | Moody's, Aaa Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 5.20%
C000193017 [Member] | Not rated [Member]  
Holdings [Line Items]  
Percent of Total Investments 13.10%
C000193017 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.50%
C000193017 [Member] | Standard & Poor's, AA Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 44.60%
C000193017 [Member] | Standard & Poor's, A Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 22.00%
C000193017 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000193017 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000193017 [Member] | Healthcare Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 12.20%
C000193017 [Member] | Transportation Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.80%
C000193017 [Member] | Education [Member]  
Holdings [Line Items]  
Percent of Total Investments 10.00%
C000193017 [Member] | Airport [Member]  
Holdings [Line Items]  
Percent of Total Investments 8.50%
C000193017 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000193017 [Member] | Facilities [Member]  
Holdings [Line Items]  
Percent of Total Investments 7.20%
C000193017 [Member] | Water And Sewer [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.50%
C000193017 [Member] | Housing [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.20%
C000193017 [Member] | Development [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000193017 [Member] | Tobacco [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.60%
C000193017 [Member] | Equity [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.40%
C000193017 [Member] | Revenue bonds [Member]  
Holdings [Line Items]  
Percent of Total Investments 76.60%
C000193017 [Member] | General obligation bonds [Member]  
Holdings [Line Items]  
Percent of Total Investments 23.00%
C000193017 [Member] | Other revenue [Member]  
Holdings [Line Items]  
Percent of Total Investments 16.30%
C000193017 [Member] | Closed End Funds [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.40%
C000001742 [Member] | CCC and below [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.50%
C000001742 [Member] | Moody's, Aaa Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 5.20%
C000001742 [Member] | Not rated [Member]  
Holdings [Line Items]  
Percent of Total Investments 13.10%
C000001742 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.50%
C000001742 [Member] | Standard & Poor's, AA Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 44.60%
C000001742 [Member] | Standard & Poor's, A Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 22.00%
C000001742 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000001742 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000001742 [Member] | Healthcare Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 12.20%
C000001742 [Member] | Transportation Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.80%
C000001742 [Member] | Education [Member]  
Holdings [Line Items]  
Percent of Total Investments 10.00%
C000001742 [Member] | Airport [Member]  
Holdings [Line Items]  
Percent of Total Investments 8.50%
C000001742 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000001742 [Member] | Facilities [Member]  
Holdings [Line Items]  
Percent of Total Investments 7.20%
C000001742 [Member] | Water And Sewer [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.50%
C000001742 [Member] | Housing [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.20%
C000001742 [Member] | Development [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000001742 [Member] | Tobacco [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.60%
C000001742 [Member] | Equity [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.40%
C000001742 [Member] | Revenue bonds [Member]  
Holdings [Line Items]  
Percent of Total Investments 76.60%
C000001742 [Member] | General obligation bonds [Member]  
Holdings [Line Items]  
Percent of Total Investments 23.00%
C000001742 [Member] | Other revenue [Member]  
Holdings [Line Items]  
Percent of Total Investments 16.30%
C000001742 [Member] | Closed End Funds [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.40%
C000001744 [Member] | CCC and below [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.50%
C000001744 [Member] | Moody's, Aaa Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 5.20%
C000001744 [Member] | Not rated [Member]  
Holdings [Line Items]  
Percent of Total Investments 13.10%
C000001744 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.50%
C000001744 [Member] | Standard & Poor's, AA Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 44.60%
C000001744 [Member] | Standard & Poor's, A Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 22.00%
C000001744 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000001744 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000001744 [Member] | Healthcare Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 12.20%
C000001744 [Member] | Transportation Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.80%
C000001744 [Member] | Education [Member]  
Holdings [Line Items]  
Percent of Total Investments 10.00%
C000001744 [Member] | Airport [Member]  
Holdings [Line Items]  
Percent of Total Investments 8.50%
C000001744 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000001744 [Member] | Facilities [Member]  
Holdings [Line Items]  
Percent of Total Investments 7.20%
C000001744 [Member] | Water And Sewer [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.50%
C000001744 [Member] | Housing [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.20%
C000001744 [Member] | Development [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000001744 [Member] | Tobacco [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.60%
C000001744 [Member] | Equity [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.40%
C000001744 [Member] | Revenue bonds [Member]  
Holdings [Line Items]  
Percent of Total Investments 76.60%
C000001744 [Member] | General obligation bonds [Member]  
Holdings [Line Items]  
Percent of Total Investments 23.00%
C000001744 [Member] | Other revenue [Member]  
Holdings [Line Items]  
Percent of Total Investments 16.30%
C000001744 [Member] | Closed End Funds [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.40%
C000178768 [Member] | CCC and below [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.50%
C000178768 [Member] | Moody's, Aaa Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 5.20%
C000178768 [Member] | Not rated [Member]  
Holdings [Line Items]  
Percent of Total Investments 13.10%
C000178768 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.50%
C000178768 [Member] | Standard & Poor's, AA Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 44.60%
C000178768 [Member] | Standard & Poor's, A Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 22.00%
C000178768 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000178768 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000178768 [Member] | Healthcare Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 12.20%
C000178768 [Member] | Transportation Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.80%
C000178768 [Member] | Education [Member]  
Holdings [Line Items]  
Percent of Total Investments 10.00%
C000178768 [Member] | Airport [Member]  
Holdings [Line Items]  
Percent of Total Investments 8.50%
C000178768 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000178768 [Member] | Facilities [Member]  
Holdings [Line Items]  
Percent of Total Investments 7.20%
C000178768 [Member] | Water And Sewer [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.50%
C000178768 [Member] | Housing [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.20%
C000178768 [Member] | Development [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000178768 [Member] | Tobacco [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.60%
C000178768 [Member] | Equity [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.40%
C000178768 [Member] | Revenue bonds [Member]  
Holdings [Line Items]  
Percent of Total Investments 76.60%
C000178768 [Member] | General obligation bonds [Member]  
Holdings [Line Items]  
Percent of Total Investments 23.00%
C000178768 [Member] | Other revenue [Member]  
Holdings [Line Items]  
Percent of Total Investments 16.30%
C000178768 [Member] | Closed End Funds [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.40%