Mid-Cap Index Portfolio 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 |
|
| Portfolio [Member] | Mid-Cap Index Portfolio | Mid-Cap Index Portfolio | ||||||||
| Prospectus [Line Items] | ||||||||
| Annual Return [Percent] | 11.54% | 15.08% | 15.83% | (18.82%) | 24.36% | 18.07% | 30.87% | (9.33%) |