S000010030 [Member] Annual Total Returns |
12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| The Bond Fund | Shares | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 7.11% | 2.05% | 6.58% | (12.71%) | (0.55%) | 7.12% | 8.96% | (0.59%) | 4.54% | 3.97% |