Vanguard Intermediate-Term Bond Index Fund Average Annual Total Returns - Institutional Prospectus [Member]	12 Months Ended	60 Months Ended	120 Months Ended
	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2025
Bloomberg U.S. 5-10 Year Gov/Credit Float Adjusted Index (reflects no deduction for fees, expenses, or taxes)[Member]
Prospectus [Line Items]
Average Annual Return, Percent	8.76%	(0.15%)	2.55%
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%
Institutional Shares
Prospectus [Line Items]
Average Annual Return, Percent	8.58%	(0.18%)	2.49%
Institutional Shares \| After Taxes on Distributions
Prospectus [Line Items]
Average Annual Return, Percent	6.79%	(1.48%)	1.24%
Institutional Shares \| After Taxes on Distributions and Sales
Prospectus [Line Items]
Average Annual Return, Percent	5.05%	(0.67%)	1.39%
Institutional Plus Shares
Prospectus [Line Items]
Average Annual Return, Percent	8.58%	(0.18%)	2.50%