Vanguard Extended Market Index Fund Investment Strategy - Admiral Prospectus [Member] - Vanguard Extended Market Index Fund |
Dec. 31, 2025 |
|---|---|
| Prospectus [Line Items] | |
| Strategy [Heading] | <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Investment Strategies</span> |
| Strategy Narrative [Text Block] | The Fund employs an indexing investment approach designed to track the performance of the S&P Completion Index (the “Target Index”), a broadly diversified index of stocks of small and mid-size U.S. companies. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in the stocks that make up the Target Index. The Fund invests by sampling the Target Index, meaning that it holds a range of securities that, in the aggregate, approximates the full Target Index in terms of key risk factors and other characteristics. |