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Investments - Additional Information (Detail) (USD $)
3 Months Ended
Oct. 26, 2013
Oct. 27, 2012
Jul. 27, 2013
Schedule of Available-for-sale Securities [Line Items]      
Average Balance Of Securities Lending $ 600,000,000 $ 800,000,000  
Minimum market value percentage of loaned securities, required collateral 102.00%    
Secured lending transactions outstanding 0   0
Fixed Income Securities [Member]
     
Schedule of Available-for-sale Securities [Line Items]      
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities 0    
Equity Securities [Member]
     
Schedule of Available-for-sale Securities [Line Items]      
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities $ 0