Vanguard Institutional 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 |
|
| Institutional Prospectus [Member] | Vanguard Institutional Index Fund | Institutional Shares | ||||||||
| Prospectus [Line Items] | ||||||||
| Annual Return [Percent] | 17.84% | 24.97% | 26.24% | (18.14%) | 28.67% | 18.39% | 31.46% | (4.42%) |