Investments (Additional Information) (Details) (USD $)	3 Months Ended			3 Months Ended		63 Months Ended	3 Months Ended
	Oct. 25, 2014	Oct. 26, 2013	Jul. 26, 2014	Oct. 25, 2014 VCE	Oct. 26, 2013 VCE	Oct. 25, 2014 VCE	Jan. 24, 2015 VCE Subsequent Event
Schedule of Investments [Line Items]
Impairment charges on available-for-sale investments	$ 0	$ 0
Other than temporary impairment, credit losses recognized in earnings, credit losses on debt securities held	0
Average daily balance of securities lending	1,000,000,000	600,000,000
Minimum market value percentage for collateral on loaned securities	102.00%	102.00%
Secured lending transactions outstanding	0		0
Cumulative gross investment in VCE				716,000,000		716,000,000
Equity Method Investment, Ownership Percentage				35.00%		35.00%
Losses from VCE				47,000,000	53,000,000	691,000,000
Equity method investments, carrying value	559,000,000		630,000,000	25,000,000		25,000,000
Proceeds from Sale of Equity Method Investments							$ 150,000,000
Ownership interest in cost method investment							10.00%