Shareholder Report, Average Annual Return (Details)	12 Months Ended	60 Months Ended	120 Months Ended
Shareholder Report, Average Annual Return (Details)	Jun. 30, 2025	Jun. 30, 2025	Jun. 30, 2025
C000037571 [Member]
Average Annual Return [Line Items]
Line Graph and Table Measure Name	Class A Shares with sales load
Average Annual Return, Percent	2.44%	0.95%	0.95%
C000024677 [Member]
Average Annual Return [Line Items]
Line Graph and Table Measure Name	Institutional Shares
Average Annual Return, Percent	3.73%	1.44%	1.43%
C000024678 [Member]
Average Annual Return [Line Items]
Line Graph and Table Measure Name	Service Shares
Average Annual Return, Percent	3.49%	1.18%	1.18%
Without Sales Load [Member] \| C000037571 [Member]
Average Annual Return [Line Items]
Line Graph and Table Measure Name	Class A Shares without sales load
Average Annual Return, Percent	3.48%	1.14%	1.05%
S And P Municipal Bond Index [Member]
Average Annual Return [Line Items]
Line Graph and Table Measure Name	S&P Municipal Bond Index
Average Annual Return, Percent	1.55%	0.77%	2.32%
S And P Municipal Bond Short Index [Member]
Average Annual Return [Line Items]
Line Graph and Table Measure Name	S&P Municipal Bond Short Index
Average Annual Return, Percent	3.99%	1.39%	1.56%
S And P Municipal Bond 1 5 Years Investment Grade 5 Pre Refunded Index [Member]
Average Annual Return [Line Items]
Line Graph and Table Measure Name	S&P Municipal Bond 1-5 Years Investment Grade 5% Pre-Refunded Index
Average Annual Return, Percent	4.11%	1.18%	1.59%
Morningstar US Fund Muni National Short Funds Average [Member]
Average Annual Return [Line Items]
Line Graph and Table Measure Name	Morningstar US Fund Muni National Short Funds Average
Average Annual Return, Percent	3.42%	1.38%	1.45%