Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	VANGUARD MONEY MARKET RESERVES
Prospectus Date	rr_ProspectusDate	Dec. 23, 2016
Supplement [Text Block]	moneymkt_SupplementTextBlock	[SHIP LOGO VANGUARD (R)] Vanguard Prime Money Market Fund Supplement to the Prospectus and Summary Prospectus for Admiral™ Shares Dated December 23, 2016 New Benchmark The Institutional Money Market Funds Average, a comparative benchmark for the Fund, has been replaced with the Money Market Funds Average. The new benchmark reflects the comparative money market fund sector resulting from recent money market changes.                                             Returns for the new benchmark will be included in future prospectus updates. © 2017 The Vanguard Group, Inc. All rights reserved. Vanguard Marketing Corporation, Distributor. PS 66 042017
Vanguard Prime Money Market Fund
Risk/Return:	rr_RiskReturnAbstract
Supplement [Text Block]	moneymkt_SupplementTextBlock	[SHIP LOGO VANGUARD (R)] Vanguard Prime Money Market Fund Supplement to the Prospectus and Summary Prospectus for Admiral™ Shares Dated December 23, 2016 New Benchmark The Institutional Money Market Funds Average, a comparative benchmark for the Fund, has been replaced with the Money Market Funds Average. The new benchmark reflects the comparative money market fund sector resulting from recent money market changes.                                             Returns for the new benchmark will be included in future prospectus updates. © 2017 The Vanguard Group, Inc. All rights reserved. Vanguard Marketing Corporation, Distributor. PS 66 042017