Shareholder Report, Average Annual Return (Details) |
12 Months Ended | 60 Months Ended | 110 Months Ended | 120 Months Ended |
|---|---|---|---|---|
May 31, 2025 |
May 31, 2025 |
May 31, 2025 |
May 31, 2025 |
|
| Without Sales Load [Member] | C000005534 | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 7.35% | 5.94% | 5.33% | |
| Without Sales Load [Member] | C000169940 | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 7.47% | 6.05% | 6.20% | |
| 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%) | 1.40% | |
| Morningstar Moderately Conservative Target Risk Index | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 9.01% | 4.95% | 4.98% | |
| Morningstar Moderately Conservative Target Risk Index | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 9.01% | 4.95% | 5.58% |