Shareholder Fees (USD $)	12 Months Ended
Aug. 31, 2013
Vanguard Federal Money Market Fund \| Vanguard Federal Money Market Fund - Investor 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 certain fund account balances below $10,000)	$ 20
Vanguard Prime Money Market Fund \| Vanguard Prime Money Market Fund - Investor 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 certain fund account balances below $10,000)	20
Vanguard Prime Money Market Fund \| Vanguard Prime Money Market 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 certain fund account balances below $10,000)	$ 20

Include the caption "Maximum Account Fees" only if the Fund charges these fees. A Fund may omit other captions if the Fund does not charge the fees or expenses covered by the captions. Disclose account fees that may be charged to a typical investor in the Fund; fees that apply to only a limited number of shareholders based on their particular circumstances need not be disclosed. Include a caption describing the maximum account fee (e.g., "Maximum Account Maintenance Fee" or "Maximum Cash Management Fee"). State the maximum annual account fee as either a fixed dollar amount or a percentage of assets. Include in a parenthetical to the caption the basis on which any percentage is calculated. If an account fee is charged only to accounts that do not meet a certain threshold (e.g., accounts under $5)

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

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Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price). If a sales charge (load) is imposed on shares purchased with reinvested capital gains distributions or returns of capital, include the bracketed words in the third caption.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

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-Section 3

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

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-Number N-1A

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-Section 3

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Maximum Sales Charge (Load) Imposed on Reinvested Dividends[and other Distributions] (as a percentage of ____)

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Form

-Number N-1A

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"Redemption Fee" (as a percentage of amount redeemed, if applicable) If the Fund is an Exchange-Traded Fund and issues or redeems shares in creation units of not less than 25,000 shares each, exclude any fees charged for the purchase and redemption of the Fund's creation units. "Redemption Fee" includes a fee charged for any redemption of the Fund's shares, but does not include a deferred sales charge (load) imposed upon redemption.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Form

-Number N-1A

-Chapter A

-Section 3

-Subsection instructions

-Paragraph 2

-Subparagraph b

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