v3.25.2
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, 2015
Jun. 30, 2025
Jun. 30, 2016
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
C000006121 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Institutional Shares                    
Accumulated Value $ 10,000   $ 10,668 $ 10,668 $ 10,905 $ 11,535 $ 11,826 $ 12,486 $ 11,252 $ 11,619 $ 12,039 $ 12,121
C000100249 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Service Shares                    
Accumulated Value 10,000   10,647 10,622 10,833 11,431 11,701 12,314 11,069 11,402 11,785 11,835
C000006118 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor A Shares (with sales charge)                    
C000038033 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor C Shares (with sales charge)                    
C000100250 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class K Shares                    
Accumulated Value 10,000   10,670 10,676 10,920 11,555 11,864 12,521 11,289 11,675 12,091 12,179
C000006125 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Institutional Shares                    
Accumulated Value 10,000   10,115 10,125 10,197 10,434 10,587 10,682 10,356 10,544 10,969 11,409
C000038034 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor A Shares (with sales charge)                    
C000006122 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor A1 Shares                    
Accumulated Value 10,000   10,103 10,103 10,164 10,390 10,532 10,616 10,282 10,448 10,868 11,294
C000006124 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Investor C Shares (with sales charge)                    
C000038035 [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Class K Shares                    
Accumulated Value 10,000   10,113 10,126 10,203 10,445 10,604 10,705 10,383 10,577 11,008 11,456
Bloomberg Municipal Bond Index [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Bloomberg Municipal Bond Index                    
Accumulated Value 10,000   10,765 10,713 10,880 11,610 12,126 12,632 11,549 11,917 12,300 12,437
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   $ 10,220 $ 10,268 $ 10,330 $ 10,689 $ 11,006 $ 11,157 $ 10,798 $ 10,914 $ 11,211 $ 11,661
Short Term Customized Reference Benchmark [Member]                        
Account Value [Line Items]                        
Line Graph and Table Measure Name   Short-Term Customized Reference Benchmark