Investments - Additional Information (Detail) (USD $)	12 Months Ended
Jul. 28, 2012	Jul. 30, 2011
Schedule of Investments [Line Items]
Average daily balance of securities lending	$ 500,000,000	$ 1,600,000,000
Minimum market value percentage for collateral on loaned securities	102.00%
Secured lending transactions outstanding	0	0
Available-For-Sale Investments
Schedule of Investments [Line Items]
Impairment charges	$ 0

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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+ Details