Annual Fund Operating Expenses	18 Months Ended
	Feb. 28, 2013
Vanguard Mega Cap Index Fund - Institutional Shares | Vanguard Mega Cap Index Fund
Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.05%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.08%
Vanguard Mega Cap Growth Index Fund - Institutional Shares | Vanguard Mega Cap Growth Index Fund
Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.06%
12b-1 Distribution Fee	none
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.09%
Vanguard Mega Cap Value Index Fund - Institutional Shares | Vanguard Mega Cap Value Index Fund
Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.04%
12b-1 Distribution Fee	none
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.08%
Vanguard Mega Cap Index Fund - ETF Shares | Vanguard Mega Cap Index Fund
Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.08%
12b-1 Distribution Fee	none
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.12%
Vanguard Mega Cap Growth Index Fund - ETF Shares | Vanguard Mega Cap Growth Index Fund
Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.08%
12b-1 Distribution Fee	none
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.12%
Vanguard Mega Cap Value Index Fund - ETF Shares | Vanguard Mega Cap Value Index Fund
Annual Fund Operating Expenses (Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.08%
12b-1 Distribution Fee	none
Other Expenses	0.04%
Total Annual Fund Operating Expenses	0.12%