Vanguard Intermediate-Term Treasury Index Fund Average Annual Total Returns - Institutional 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%
Institutional Shares
Prospectus [Line Items]
Average Annual Return, Percent	1.27%	(0.18%)	1.10%
Institutional Shares \| After Taxes on Distributions
Prospectus [Line Items]
Average Annual Return, Percent	(0.21%)	(1.11%)	0.23%
Institutional Shares \| After Taxes on Distributions and Sales
Prospectus [Line Items]
Average Annual Return, Percent	0.75%	(0.50%)	0.48%