Expense Example, No Redemption (Vanguard Federal Money Market Fund - Investor Shares, Vanguard Federal Money Market Fund, USD $)	12 Months Ended
Aug. 31, 2011
Vanguard Federal Money Market Fund - Investor Shares \| Vanguard Federal Money Market Fund
Expense Example, No Redemption:
1 YEAR	$ 20
3 YEAR	64
5 YEAR	113
10 YEAR	$ 255

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You would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.

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Reference 1: 1

-Publisher SEC

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-Number N-1A

-Chapter A

-Section 3

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Reference 1: 1

-Publisher SEC

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Reference 1: 1

-Publisher SEC

-Name Form

-Number N-1A

-Chapter A

-Section 3

-Paragraph 4

-Subparagraph f

-Subsection instructions

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Data Type:	rr:NonNegativeMonetaryType
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