S000001260 [Member] Average Annual Total Returns |
12 Months Ended | 60 Months Ended | 120 Months Ended |
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2025 |
|
| Bloomberg U.S. Municipal Bond Index (reflects no deduction for fees, expenses, or taxes) | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 4.25% | 0.80% | 2.34% |
| TAX-EXEMPT FUND | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 3.93% | 0.17% | 1.91% |
| TAX-EXEMPT FUND | After Taxes on Distributions | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 3.91% | 0.10% | 1.83% |
| TAX-EXEMPT FUND | After Taxes on Distributions and Sales | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 3.80% | 0.77% | 2.10% |