Investments - Additional Information (Detail) (USD $) In Millions	Jun. 30, 2011	Jun. 30, 2010
Schedule of Cost-method Investments [Line Items]
Recorded basis of common and preferred stock and other investments that are restricted for more than one year or are not publicly traded	$ 334	$ 216
Estimated fair value of common and preferred stock and other investments that are restricted for more than one year or are not publicly traded	$ 334	$ 216

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msft_RestrictedOrNonPubliclyTradedLongTermEquityInvestmentsAtFairValue

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msft

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xbrli:monetaryItemType

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debit

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instant