Vanguard Mega Cap Growth Index Fund Annual Fund Operating Expenses - Institutional [Member] - Vanguard Mega Cap Growth Index Fund - Institutional Shares	Sep. 30, 2025
Prospectus [Line Items]
Management Fees (as a percentage of Assets)	0.05%
Distribution and Service (12b-1) Fees	0.00%
Other Expenses (as a percentage of Assets):	0.01%
Expenses (as a percentage of Assets)	0.06%

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