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S000000286 [Member] Average Annual Total Returns
 12 Months Ended 60 Months Ended 114 Months Ended 120 Months Ended 143 Months Ended 347 Months Ended 447 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
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Dec. 31, 2025
Lipper General & Insured Municipal Debt Funds Classification Average (reflects no deduction for taxes or sales loads)              
Prospectus [Line Items]              
Average Annual Return, Percent [1] 3.35% 0.56%   2.13%      
S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)              
Prospectus [Line Items]              
Average Annual Return, Percent [2] 4.26% 1.06%   2.44%      
Class A              
Prospectus [Line Items]              
Average Annual Return, Percent (1.53%) (1.34%)   1.55%    
Performance Inception Date             Oct. 03, 1988
Class A | After Taxes on Distributions              
Prospectus [Line Items]              
Average Annual Return, Percent (1.55%) (1.36%)   1.54%    
Performance Inception Date             Oct. 03, 1988
Class A | After Taxes on Distributions and Sales              
Prospectus [Line Items]              
Average Annual Return, Percent 0.73% (0.26%)   1.98%    
Performance Inception Date             Oct. 03, 1988
Class I              
Prospectus [Line Items]              
Average Annual Return, Percent 3.00% (0.29%)   2.19%    
Performance Inception Date           Feb. 06, 1997  
Class C              
Prospectus [Line Items]              
Average Annual Return, Percent 1.95% (1.29%)   1.34%    
Performance Inception Date         Feb. 10, 2014    
Class R6              
Prospectus [Line Items]              
Average Annual Return, Percent 3.03% (0.26%) 1.75%      
Performance Inception Date     Jun. 30, 2016        
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 [1]     1.75%        
Class R6 | S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)              
Prospectus [Line Items]              
Average Annual Return, Percent [2]     2.11%        
[1]
Represents the average annualized total return for all reporting funds in the Lipper General & Insured Municipal Debt Funds Classification.
[2]
An index designed to measure the performance of the tax-exempt U.S. municipal bond market.