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Shareholder Fees (Vanguard Mega Cap Index Fund ETF)
Vanguard Mega Cap Index Fund
Vanguard Mega Cap Index Fund - ETF Shares
9/1/2013 - 8/31/2014
Shareholder Fees (fees paid directly from your investment]  
Transaction Fee on Conversion to ETF Shares 0vanguard_ETFConversionFee
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/ rr_ProspectusShareClassAxis
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Transaction Fee On Purchases and Sales 0vanguard_TransactionFeeOnPurchases
/ dei_LegalEntityAxis
= vanguard_S000019698Member
/ rr_ProspectusShareClassAxis
= vanguard_C000055210Member
Transaction Fee On Reinvested Dividends 0vanguard_TransactionFeeOnReinvestedDividends
/ dei_LegalEntityAxis
= vanguard_S000019698Member
/ rr_ProspectusShareClassAxis
= vanguard_C000055210Member