Vanguard Intermediate-Term Treasury Index Fund Average Annual Total Returns - Admiral Prospectus [Member]	12 Months Ended	60 Months Ended	120 Months Ended
	Dec. 31, 2024	Dec. 31, 2024	Dec. 31, 2024
Bloomberg U.S. Treasury 3-10 Year Index (reflects no deduction for fees, expenses, or taxes)[Member]
Prospectus [Line Items]
Average Annual Return, Percent	1.26%	(0.16%)	1.14%
Spliced Bloomberg U.S. Treasury 3-10 Year Index in USD (reflects no deduction for fees, expenses, or taxes)[Member]
Prospectus [Line Items]
Average Annual Return, Percent	1.26%	(0.16%)	1.14%
Bloomberg U.S. Aggregate Float Adjusted Index (reflects no deduction for fees, expenses, or taxes)[Member]
Prospectus [Line Items]
Average Annual Return, Percent	1.33%	(0.27%)	1.39%
Admiral Shares
Prospectus [Line Items]
Average Annual Return, Percent	1.29%	(0.20%)	1.08%
Admiral Shares \| After Taxes on Distributions
Prospectus [Line Items]
Average Annual Return, Percent	(0.19%)	(1.12%)	0.22%
Admiral Shares \| After Taxes on Distributions and Sales
Prospectus [Line Items]
Average Annual Return, Percent	0.76%	(0.51%)	0.47%