Investments (Additional Information) (Details)	12 Months Ended
	Jul. 28, 2018 USD ($) entity	Jul. 29, 2017 USD ($)	Jul. 30, 2016 USD ($)
Investments, Debt and Equity Securities [Abstract]
Net unsettled available-for-sale investments, purchases	$ 1,500,000,000	$ 30,000,000
Impairment charges of available-for-sale investments	52,000,000	74,000,000	$ 3,000,000
Other than temporary impairment, credit losses recognized in earnings, credit losses on debt securities held	0
Average daily balance of securities lending	$ 300,000,000	700,000,000
Minimum market value percentage for collateral on loaned securities (at least)	102.00%
Secured lending transactions outstanding	$ 0	0
Number of variable interest entities required to be consolidated (entity) | entity	0
Variable Interest Entity [Line Items]
Investments in privately held companies	$ 1,096,000,000	$ 983,000,000
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Investments in privately held companies	531,000,000
Funding commitments	$ 223,000,000