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
Jun. 30, 2016
Jun. 30, 2026
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2022
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2026
C000100250 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class K Shares                    
Accumulated Value $ 10,000   $ 10,006 $ 10,234 $ 10,830 $ 11,119 $ 11,735 $ 10,580 $ 10,942 $ 11,332 $ 11,415 $ 12,147
C000038033 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor C Shares (with sales charge)                    
Accumulated Value 10,000   9,913 10,034 10,498 10,666 11,149 9,948 10,170 10,433 10,468 11,106
C000006118 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor A Shares (with sales charge)                    
Accumulated Value 9,575   9,554 9,751 10,279 10,521 11,071 9,952 10,261 10,606 10,640 11,289
C000100249 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Service Shares                    
Accumulated Value 10,000   9,977 10,175 10,736 10,990 11,566 10,396 10,709 11,069 11,116 11,794
C000006121 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Institutional Shares                    
Accumulated Value 10,000   10,000 10,222 10,812 11,085 11,704 10,547 10,891 11,285 11,362 12,085
C000006125 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Institutional Shares                    
Accumulated Value 10,000   10,010 10,081 10,315 10,466 10,561 10,238 10,424 10,844 11,279 11,771
C000038034 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor A Shares (with sales charge)                    
Accumulated Value 9,700   9,694 9,730 9,932 10,064 10,130 9,798 9,943 10,329 10,708 11,159
C000006122 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor A1 Shares                    
Accumulated Value 10,000   10,000 10,060 10,284 10,425 10,508 10,177 10,341 10,758 11,179 11,654
C000006124 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor C Shares (with sales charge)                    
Accumulated Value 10,000   9,914 9,878 10,008 10,055 10,045 9,638 9,715 10,008 10,374 10,811
C000038035 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class K Shares                    
Accumulated Value 10,000   10,013 10,089 10,328 10,485 10,585 10,266 10,459 10,885 11,328 11,827
Bloomberg Municipal Bond Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Bloomberg Municipal Bond Index                    
Accumulated Value 10,000   9,951 10,107 10,785 11,264 11,734 10,728 11,070 11,425 11,553 12,365
Bloomberg Municipal 1 5 Year Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Bloomberg Municipal 1-5 Year Index                    
Accumulated Value $ 10,000   $ 10,047 $ 10,108 $ 10,459 $ 10,769 $ 10,917 $ 10,565 $ 10,679 $ 10,970 $ 11,410 $ 11,789