Shareholder Fees (USD $)	18 Months Ended
	Feb. 28, 2013
Vanguard Mega Cap Growth Index Fund | Vanguard Mega Cap Growth Index Fund - Institutional Shares
Shareholder Fees (fees paid directly from your investment]
Sales charge (load) imposed on purchases	none
Purchase Fee	none
Sales charge (load) imposed on reinvested dividends	none
Redemption Fee	none
Account Service Fee (for fund account balances below $10,000)	$ 20
Vanguard Mega Cap Growth Index Fund | Vanguard Mega Cap Growth Index Fund - ETF Shares
Shareholder Fees (fees paid directly from your investment]
Transaction Fee on Conversion to ETF Shares	0
Transaction Fee On Purchases and Sales	0
Transaction Fee On Reinvested Dividends	0
Vanguard Mega Cap Index Fund | Vanguard Mega Cap Index Fund - Institutional Shares
Shareholder Fees (fees paid directly from your investment]
Sales charge (load) imposed on purchases	none
Purchase Fee	none
Sales charge (load) imposed on reinvested dividends	none
Redemption Fee	none
Account Service Fee (for fund account balances below $10,000)	20
Vanguard Mega Cap Index Fund | Vanguard Mega Cap Index Fund - ETF Shares
Shareholder Fees (fees paid directly from your investment]
Transaction Fee on Conversion to ETF Shares	0
Transaction Fee On Purchases and Sales	0
Transaction Fee On Reinvested Dividends	0
Vanguard Mega Cap Value Index Fund | Vanguard Mega Cap Value Index Fund - Institutional Shares
Shareholder Fees (fees paid directly from your investment]
Sales charge (load) imposed on purchases	none
Purchase Fee	none
Sales charge (load) imposed on reinvested dividends	none
Redemption Fee	none
Account Service Fee (for fund account balances below $10,000)	$ 20
Vanguard Mega Cap Value Index Fund | Vanguard Mega Cap Value Index Fund - ETF Shares
Shareholder Fees (fees paid directly from your investment]
Transaction Fee on Conversion to ETF Shares	0
Transaction Fee On Purchases and Sales	0
Transaction Fee On Reinvested Dividends	0