Mid Cap Index Fund 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 |
|
| Mid Cap Index Fund | None | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 6.95% | 13.51% | 15.94% | (13.35%) | 24.32% | 13.30% | 25.71% | (11.43%) | 15.91% | 20.62% |