v3.25.2
S000000286 [Member] Average Annual Total Returns
 12 Months Ended 60 Months Ended 102 Months Ended 120 Months Ended 131 Months Ended 335 Months Ended 435 Months Ended
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)              
Prospectus [Line Items]              
Average Annual Return, Percent [1] 1.90% 1.20%   2.34%      
Lipper General & Insured Municipal Debt Funds Classification Average (reflects no deduction for taxes or sales loads)              
Prospectus [Line Items]              
Average Annual Return, Percent [2] 2.27% 0.82%   2.07%      
Class A              
Prospectus [Line Items]              
Average Annual Return, Percent (1.76%) (0.80%)   1.65%    
Performance Inception Date             Oct. 03, 1988
Class A | After Taxes on Distributions              
Prospectus [Line Items]              
Average Annual Return, Percent (1.77%) (0.81%)   1.64%    
Performance Inception Date             Oct. 03, 1988
Class A | After Taxes on Distributions and Sales              
Prospectus [Line Items]              
Average Annual Return, Percent 0.45% 0.14%   2.06%    
Performance Inception Date             Oct. 03, 1988
Class C              
Prospectus [Line Items]              
Average Annual Return, Percent 1.78% (0.75%)   1.43%    
Performance Inception Date         Feb. 10, 2014    
Class R6              
Prospectus [Line Items]              
Average Annual Return, Percent 2.85% 0.26% 1.60%      
Performance Inception Date     Jun. 30, 2016        
Class R6 | S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)              
Prospectus [Line Items]              
Average Annual Return, Percent [1]     1.86%        
Class R6 | Lipper General & Insured Municipal Debt Funds Classification Average (reflects no deduction for taxes or sales loads)              
Prospectus [Line Items]              
Average Annual Return, Percent [2]     1.54%        
Class I              
Prospectus [Line Items]              
Average Annual Return, Percent 2.80% 0.23%   2.30%    
Performance Inception Date           Feb. 06, 1997  
[1]
An index designed to measure the performance of the tax-exempt U.S. municipal bond market.
[2]
Represents the average annualized total return for all reporting funds in the Lipper General & Insured Municipal Debt Funds Classification.