Vanguard Extended Market Index Fund Average Annual Total Returns - Admiral 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% |
| Admiral Shares | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 11.42% | 6.19% | 11.01% |
| Admiral Shares | After Taxes on Distributions | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 11.06% | 5.85% | 10.60% |
| Admiral Shares | After Taxes on Distributions and Sales | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 6.92% | 4.75% | 8.98% |