Shareholder Report, Average Annual Return (Details) |
12 Months Ended | 60 Months Ended | 104 Months Ended | 120 Months Ended |
|---|---|---|---|---|
Feb. 28, 2026 |
Feb. 28, 2026 |
Feb. 28, 2026 |
Feb. 28, 2026 |
|
| Without Sales Load [Member] | C000005541 | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 3.96% | 1.29% | 2.23% | |
| Without Sales Load [Member] | C000193180 | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 4.09% | 1.41% | 2.42% | |
| Bloomberg Municipal Bond Index | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 4.96% | 1.44% | 2.43% | |
| Bloomberg Municipal Bond Index | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 4.96% | 1.44% | 2.54% |