v3.26.1
Shareholder Report, Line Graph (Details) - USD ($)
 12 Months Ended 24 Months Ended 36 Months Ended 48 Months Ended 60 Months Ended 72 Months Ended 84 Months Ended 96 Months Ended 108 Months Ended 120 Months Ended
May 31, 2016
May 31, 2026
May 31, 2017
May 31, 2018
May 31, 2019
May 31, 2020
May 31, 2021
May 31, 2022
May 31, 2023
May 31, 2024
May 31, 2025
May 31, 2026
C000001376 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   with Maximum Deferred Sales Charge - 1.00%                    
Accumulated Value $ 10,000   $ 9,948 $ 9,967 $ 10,334 $ 10,460 $ 10,928 $ 9,974 $ 9,858 $ 10,076 $ 10,084 $ 10,609
C000001378 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   with Maximum Sales Charge - 4.50%                    
Accumulated Value 9,550   9,573 9,671 10,096 10,304 10,848 9,971 9,933 10,233 10,321 10,959
C000000023 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class Z                    
Accumulated Value 10,000   10,047 10,171 10,641 10,885 11,484 10,579 10,560 10,902 11,018 11,722
C000130450 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class Y                    
Accumulated Value 1,000,000   1,005,163 1,018,261 1,066,607 1,090,925 1,151,343 1,058,562 1,055,514 1,089,464 1,102,259 1,173,900
C000073387 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class I                    
Accumulated Value 10,000   10,049 10,177 10,658 10,898 11,500 10,595 10,588 10,926 11,046 11,756
Bloomberg U S Municipal Bond C000130450 Index [Member]                        
Account Value [Line Items]                        
Accumulated Value 1,000,000   1,014,600 1,025,862 1,091,517 1,134,960 1,188,757 1,108,040 1,113,470 1,143,199 1,166,406 1,244,200
Bloomberg U S Municipal Bond Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Bloomberg U.S. Municipal Bond Index                    
Accumulated Value $ 10,000   $ 10,146 $ 10,259 $ 10,915 $ 11,350 $ 11,888 $ 11,080 $ 11,135 $ 11,432 $ 11,664 $ 12,442