Vanguard Extended Market Index Fund Average Annual Total Returns - Investor Prospectus [Member] |
12 Months Ended | 60 Months Ended | 120 Months Ended |
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2025 |
|
| S&P Completion Index (reflects no deduction for fees, expenses, or taxes)[Member] | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 11.32% | 6.06% | 10.89% |
| Dow Jones U.S. Total Stock Market Float Adjusted Index (reflects no deduction for fees, expenses, or taxes)[Member] | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 17.05% | 13.07% | 14.21% |
| Investor Shares | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 11.26% | 6.05% | 10.87% |
| Investor Shares | After Taxes on Distributions | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 10.94% | 5.75% | 10.50% |
| Investor Shares | After Taxes on Distributions and Sales | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 6.81% | 4.65% | 8.87% |