Vanguard Total Bond 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 |
|
| Bloomberg U.S. Aggregate Float Adjusted Index (reflects no deduction for fees, expenses, or taxes)[Member] | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 7.21% | (0.37%) | 2.05% |
| Investor Shares | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 7.03% | (0.52%) | 1.89% |
| Investor Shares | After Taxes on Distributions | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 5.40% | (1.70%) | 0.76% |
| Investor Shares | After Taxes on Distributions and Sales | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 4.14% | (0.90%) | 0.96% |