Investments (Additional Information) (Details)	6 Months Ended
	Jan. 28, 2017 USD ($) entity	Jan. 23, 2016 USD ($)	Jul. 30, 2016 USD ($)
Schedule of Investments [Line Items]
Other than temporary impairment, credit losses recognized in earnings, credit losses on debt securities held	$ 0
Average daily balance of securities lending	$ 1,500,000,000	$ 600,000,000
Fair value of securities received as collateral that can be resold or repledged, percentage (at least)	102.00%
Secured lending transactions outstanding	$ 0		$ 0
Number of variable interest entities required to be consolidated | entity	0
Investments in privately held companies	$ 1,007,000,000		$ 1,003,000,000
Funding commitments	182,000,000
Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments [Line Items]
Investments in privately held companies	$ 580,000,000