Investments - Additional Information (Detail) (USD $)	6 Months Ended			3 Months Ended		6 Months Ended
	Jan. 25, 2014	Jan. 26, 2013	Jul. 27, 2013	Jan. 25, 2014 Equity Securities [Member]	Jan. 26, 2013 Equity Securities [Member]	Jan. 25, 2014 Equity Securities [Member]	Jan. 26, 2013 Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses recognized in earnings				$ 11,000,000	$ 0	$ 11,000,000	$ 0
Average Balance Of Securities Lending	900,000,000	800,000,000
Minimum market value percentage of loaned securities, required collateral (Percentage)	102.00%
Secured lending transactions outstanding	$ 0		$ 0