Available-for-Sale Debt Investments and Equity Investments (Summary of Available-for-Sale Investments) (Details) - USD ($) $ in Millions	Oct. 27, 2018	Jul. 28, 2018
Schedule of Investments [Line Items]
Amortized Cost	$ 34,689	$ 37,512
Gross Unrealized Gains	33	44
Gross Unrealized Losses	(539)	(547)
Fair Value	34,183	37,009
Net unsettled, available-for-sale investments purchases (sales), net	1	(1,500)
U.S. government securities
Schedule of Investments [Line Items]
Amortized Cost	5,783	7,318
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(29)	(43)
Fair Value	5,754	7,275
U.S. government agency securities
Schedule of Investments [Line Items]
Amortized Cost	434	732
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4)	(5)
Fair Value	430	727
Non-U.S. government and agency securities
Schedule of Investments [Line Items]
Amortized Cost	153	209
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Fair Value	153	208
Corporate debt securities
Schedule of Investments [Line Items]
Amortized Cost	26,444	27,765
Gross Unrealized Gains	33	44
Gross Unrealized Losses	(446)	(445)
Fair Value	26,031	27,364
U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	1,481	1,488
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(60)	(53)
Fair Value	1,421	$ 1,435
Commercial paper
Schedule of Investments [Line Items]
Amortized Cost	309
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	309
Certificates of deposit
Schedule of Investments [Line Items]
Amortized Cost	85
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	$ 85