v3.26.3
Shareholder Report, Holdings (Details)
Aug. 31, 2026
C000074146 [Member] | WISCONSIN  
Holdings [Line Items]  
Percent of Net Asset Value 3.52%
C000074146 [Member] | ARIZONA  
Holdings [Line Items]  
Percent of Net Asset Value 4.58%
C000074146 [Member] | PUERTO RICO  
Holdings [Line Items]  
Percent of Net Asset Value 14.00%
C000074146 [Member] | ALABAMA  
Holdings [Line Items]  
Percent of Net Asset Value 3.69%
C000074146 [Member] | CALIFORNIA  
Holdings [Line Items]  
Percent of Net Asset Value 10.02%
C000074146 [Member] | FLORIDA  
Holdings [Line Items]  
Percent of Net Asset Value 5.95%
C000074146 [Member] | ILLINOIS  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
C000074146 [Member] | NEW JERSEY  
Holdings [Line Items]  
Percent of Net Asset Value 3.56%
C000074146 [Member] | NEW YORK  
Holdings [Line Items]  
Percent of Net Asset Value 9.55%
C000074146 [Member] | TEXAS  
Holdings [Line Items]  
Percent of Net Asset Value 5.91%
C000074146 [Member] | Water And Sewer Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 2.37%
C000074146 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 14.99%
C000074146 [Member] | Special Tax Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.63%
C000074146 [Member] | Transportation Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 13.60%
C000074146 [Member] | Healthcare Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 11.48%
C000074146 [Member] | Education Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 11.87%
C000074146 [Member] | Lease Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.52%
C000074146 [Member] | State General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.40%
C000074146 [Member] | Electric Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 3.26%
C000074146 [Member] | Local General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 4.36%
C000006387 [Member] | WISCONSIN  
Holdings [Line Items]  
Percent of Net Asset Value 3.52%
C000006387 [Member] | ARIZONA  
Holdings [Line Items]  
Percent of Net Asset Value 4.58%
C000006387 [Member] | PUERTO RICO  
Holdings [Line Items]  
Percent of Net Asset Value 14.00%
C000006387 [Member] | ALABAMA  
Holdings [Line Items]  
Percent of Net Asset Value 3.69%
C000006387 [Member] | CALIFORNIA  
Holdings [Line Items]  
Percent of Net Asset Value 10.02%
C000006387 [Member] | FLORIDA  
Holdings [Line Items]  
Percent of Net Asset Value 5.95%
C000006387 [Member] | ILLINOIS  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
C000006387 [Member] | NEW JERSEY  
Holdings [Line Items]  
Percent of Net Asset Value 3.56%
C000006387 [Member] | NEW YORK  
Holdings [Line Items]  
Percent of Net Asset Value 9.55%
C000006387 [Member] | TEXAS  
Holdings [Line Items]  
Percent of Net Asset Value 5.91%
C000006387 [Member] | Water And Sewer Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 2.37%
C000006387 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 14.99%
C000006387 [Member] | Special Tax Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.63%
C000006387 [Member] | Transportation Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 13.60%
C000006387 [Member] | Healthcare Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 11.48%
C000006387 [Member] | Education Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 11.87%
C000006387 [Member] | Lease Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.52%
C000006387 [Member] | State General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.40%
C000006387 [Member] | Electric Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 3.26%
C000006387 [Member] | Local General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 4.36%
C000006385 [Member] | WISCONSIN  
Holdings [Line Items]  
Percent of Net Asset Value 3.52%
C000006385 [Member] | ARIZONA  
Holdings [Line Items]  
Percent of Net Asset Value 4.58%
C000006385 [Member] | PUERTO RICO  
Holdings [Line Items]  
Percent of Net Asset Value 14.00%
C000006385 [Member] | ALABAMA  
Holdings [Line Items]  
Percent of Net Asset Value 3.69%
C000006385 [Member] | CALIFORNIA  
Holdings [Line Items]  
Percent of Net Asset Value 10.02%
C000006385 [Member] | FLORIDA  
Holdings [Line Items]  
Percent of Net Asset Value 5.95%
C000006385 [Member] | ILLINOIS  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
C000006385 [Member] | NEW JERSEY  
Holdings [Line Items]  
Percent of Net Asset Value 3.56%
C000006385 [Member] | NEW YORK  
Holdings [Line Items]  
Percent of Net Asset Value 9.55%
C000006385 [Member] | TEXAS  
Holdings [Line Items]  
Percent of Net Asset Value 5.91%
C000006385 [Member] | Water And Sewer Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 2.37%
C000006385 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 14.99%
C000006385 [Member] | Special Tax Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.63%
C000006385 [Member] | Transportation Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 13.60%
C000006385 [Member] | Healthcare Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 11.48%
C000006385 [Member] | Education Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 11.87%
C000006385 [Member] | Lease Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.52%
C000006385 [Member] | State General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.40%
C000006385 [Member] | Electric Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 3.26%
C000006385 [Member] | Local General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 4.36%
C000006388 [Member] | PUERTO RICO  
Holdings [Line Items]  
Percent of Net Asset Value 11.20%
C000006388 [Member] | ALABAMA  
Holdings [Line Items]  
Percent of Net Asset Value 4.67%
C000006388 [Member] | CALIFORNIA  
Holdings [Line Items]  
Percent of Net Asset Value 10.27%
C000006388 [Member] | COLORADO  
Holdings [Line Items]  
Percent of Net Asset Value 4.48%
C000006388 [Member] | FLORIDA  
Holdings [Line Items]  
Percent of Net Asset Value 7.91%
C000006388 [Member] | ILLINOIS  
Holdings [Line Items]  
Percent of Net Asset Value 9.16%
C000006388 [Member] | NEW JERSEY  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
C000006388 [Member] | NEW YORK  
Holdings [Line Items]  
Percent of Net Asset Value 14.07%
C000006388 [Member] | PENNSYLVANIA  
Holdings [Line Items]  
Percent of Net Asset Value 3.88%
C000006388 [Member] | TEXAS  
Holdings [Line Items]  
Percent of Net Asset Value 2.82%
C000006388 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 22.56%
C000006388 [Member] | Special Tax Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.09%
C000006388 [Member] | Transportation Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.58%
C000006388 [Member] | Healthcare Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.28%
C000006388 [Member] | Education Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 7.58%
C000006388 [Member] | Lease Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 6.75%
C000006388 [Member] | State General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 6.58%
C000006388 [Member] | Housing Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 5.99%
C000006388 [Member] | Electric Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 3.98%
C000006388 [Member] | Local General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 2.58%
C000006390 [Member] | PUERTO RICO  
Holdings [Line Items]  
Percent of Net Asset Value 11.20%
C000006390 [Member] | ALABAMA  
Holdings [Line Items]  
Percent of Net Asset Value 4.67%
C000006390 [Member] | CALIFORNIA  
Holdings [Line Items]  
Percent of Net Asset Value 10.27%
C000006390 [Member] | COLORADO  
Holdings [Line Items]  
Percent of Net Asset Value 4.48%
C000006390 [Member] | FLORIDA  
Holdings [Line Items]  
Percent of Net Asset Value 7.91%
C000006390 [Member] | ILLINOIS  
Holdings [Line Items]  
Percent of Net Asset Value 9.16%
C000006390 [Member] | NEW JERSEY  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
C000006390 [Member] | NEW YORK  
Holdings [Line Items]  
Percent of Net Asset Value 14.07%
C000006390 [Member] | PENNSYLVANIA  
Holdings [Line Items]  
Percent of Net Asset Value 3.88%
C000006390 [Member] | TEXAS  
Holdings [Line Items]  
Percent of Net Asset Value 2.82%
C000006390 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 22.56%
C000006390 [Member] | Special Tax Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.09%
C000006390 [Member] | Transportation Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.58%
C000006390 [Member] | Healthcare Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.28%
C000006390 [Member] | Education Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 7.58%
C000006390 [Member] | Lease Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 6.75%
C000006390 [Member] | State General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 6.58%
C000006390 [Member] | Housing Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 5.99%
C000006390 [Member] | Electric Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 3.98%
C000006390 [Member] | Local General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 2.58%
C000074147 [Member] | PUERTO RICO  
Holdings [Line Items]  
Percent of Net Asset Value 11.20%
C000074147 [Member] | ALABAMA  
Holdings [Line Items]  
Percent of Net Asset Value 4.67%
C000074147 [Member] | CALIFORNIA  
Holdings [Line Items]  
Percent of Net Asset Value 10.27%
C000074147 [Member] | COLORADO  
Holdings [Line Items]  
Percent of Net Asset Value 4.48%
C000074147 [Member] | FLORIDA  
Holdings [Line Items]  
Percent of Net Asset Value 7.91%
C000074147 [Member] | ILLINOIS  
Holdings [Line Items]  
Percent of Net Asset Value 9.16%
C000074147 [Member] | NEW JERSEY  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
C000074147 [Member] | NEW YORK  
Holdings [Line Items]  
Percent of Net Asset Value 14.07%
C000074147 [Member] | PENNSYLVANIA  
Holdings [Line Items]  
Percent of Net Asset Value 3.88%
C000074147 [Member] | TEXAS  
Holdings [Line Items]  
Percent of Net Asset Value 2.82%
C000074147 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 22.56%
C000074147 [Member] | Special Tax Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.09%
C000074147 [Member] | Transportation Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 15.58%
C000074147 [Member] | Healthcare Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.28%
C000074147 [Member] | Education Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 7.58%
C000074147 [Member] | Lease Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 6.75%
C000074147 [Member] | State General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 6.58%
C000074147 [Member] | Housing Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 5.99%
C000074147 [Member] | Electric Revenue Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 3.98%
C000074147 [Member] | Local General Obligation Bonds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 2.58%