Investments (Additional Information) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 23, 2016	Jan. 24, 2015	Jan. 23, 2016	Jan. 24, 2015	Jul. 25, 2015
Investments, Debt and Equity Securities [Abstract]
Impairment charges on available-for-sale investments	$ 3,000,000	$ 0	$ 3,000,000	$ 0
Other than temporary impairment, credit losses recognized in earnings, credit losses on debt securities held	0		0
Average daily balance of securities lending			$ 600,000,000	$ 600,000,000
Fair Value Of Securities Received As Collateral That Can Be Resold Or RePledged Percentage			102.00%	102.00%
Secured lending transactions outstanding	$ 0		$ 0		$ 0