Vanguard Long-Term Treasury Fund Average Annual Total Returns - Retail Prospectus [Member] |
12 Months Ended | 60 Months Ended | 120 Months Ended |
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2025 |
|
| Bloomberg U.S. Long Treasury Bond Index (reflects no deduction for fees, expenses, or taxes)[Member] | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 5.59% | (7.23%) | 0.02% |
| Bloomberg U.S. Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)[Member] | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 7.30% | (0.36%) | 2.01% |
| Investor Shares | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 5.54% | (7.30%) | (0.04%) |
| Investor Shares | After Taxes on Distributions | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 3.72% | (8.62%) | (1.56%) |
| Investor Shares | After Taxes on Distributions and Sales | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 3.26% | (5.76%) | (0.44%) |
| Admiral Shares | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 5.64% | (7.20%) | 0.06% |