Vanguard Mortgage-Backed Securities Index Fund Investment Objectives and Goals - Admiral Prospectus [Member] - Vanguard Mortgage-Backed Securities Index Fund |
Aug. 31, 2025 |
|---|---|
| Prospectus [Line Items] | |
| Risk/Return [Heading] | <span style="color:#000000;font-family:Arial;font-size:13pt;font-weight:bold;">Vanguard Mortgage-Backed Securities Index Fund</span> |
| Objective [Heading] | <span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Investment Objective</span> |
| Objective, Primary [Text Block] | Vanguard Mortgage-Backed Securities Index Fund (the “Fund”) seeks to track the performance of a market-weighted mortgage-backed securities index. |