Vanguard Mega Cap Growth Index Fund Investment Objectives and Goals - Institutional [Member] - Vanguard Mega Cap Growth Index Fund	Sep. 30, 2025
Prospectus [Line Items]
Risk/Return [Heading]	<span style="color:#000000;font-family:Arial;font-size:13pt;font-weight:bold;">Fund Summary</span>
Objective [Heading]	<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;">Investment Objective</span>
Objective, Primary [Text Block]	Vanguard Mega Cap Growth Index Fund (the “Fund”) seeks to track the performance of a benchmark index that measures the investment return of large-capitalization growth stocks in the United States.