Investments (Additional Information) (Details) entity in Millions	3 Months Ended		6 Months Ended
	Jan. 27, 2018 USD ($) entity	Jan. 28, 2017 USD ($)	Jan. 27, 2018 USD ($) entity	Jan. 28, 2017 USD ($)	Jul. 29, 2017 USD ($)
Schedule of Investments [Line Items]
Impairment charges of available-for-sale investments	$ 0	$ 0	$ 26,000,000	$ 0
Other than temporary impairment, credit losses recognized in earnings, credit losses on debt securities held	0		0
Average daily balance of securities lending			$ 400,000,000	$ 900,000,000
Fair value of securities received as collateral that can be resold or repledged, percentage (at least)			102.00%
Secured lending transactions outstanding	$ 0		$ 0		$ 0
Number of variable interest entities required to be consolidated (entity) | entity	0		0
Investments in privately held companies	$ 982,000,000		$ 982,000,000		$ 983,000,000
Funding commitments	215,000,000		215,000,000
Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments [Line Items]
Investments in privately held companies	$ 528,000,000		$ 528,000,000