Shareholder Report, Average Annual Return (Details) |
12 Months Ended | 60 Months Ended | 97 Months Ended | 120 Months Ended |
|---|---|---|---|---|
May 31, 2025 |
May 31, 2025 |
May 31, 2025 |
May 31, 2025 |
|
| Without Sales Load [Member] | C000005523 | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 5.02% | (1.14%) | 0.67% | |
| Without Sales Load [Member] | C000190558 | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 5.11% | (0.98%) | 0.67% | |
| Bloomberg U.S. Aggregate Bond Index | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 5.46% | (0.90%) | 1.49% | |
| Bloomberg U.S. Aggregate Bond Index | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 5.46% | (0.90%) | 1.39% | |
| Bloomberg U.S. GNMA Index | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 5.46% | (0.87%) | 1.00% | |
| Bloomberg U.S. GNMA Index | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 5.46% | (0.87%) | 0.89% |