Available-for-Sale Debt Investments and Equity Investments (Summary of Available-for-Sale Investments) (Details) - USD ($) $ in Millions	Jan. 26, 2019	Jul. 28, 2018
Schedule of Investments [Line Items]
Amortized Cost	$ 30,893	$ 37,512
Gross Unrealized Gains	17	44
Gross Unrealized Losses	(424)	(547)
Fair Value	30,486	37,009
Net unsettled, available-for-sale investments purchases (sales), net	4	(1,500)
U.S. government securities
Schedule of Investments [Line Items]
Amortized Cost	3,486	7,318
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(14)	(43)
Fair Value	3,472	7,275
U.S. government agency securities
Schedule of Investments [Line Items]
Amortized Cost	356	732
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2)	(5)
Fair Value	354	727
Non-U.S. government and agency securities
Schedule of Investments [Line Items]
Amortized Cost	115	209
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(1)
Fair Value	115	208
Corporate debt securities
Schedule of Investments [Line Items]
Amortized Cost	25,103	27,765
Gross Unrealized Gains	16	44
Gross Unrealized Losses	(366)	(445)
Fair Value	24,753	27,364
U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	1,475	1,488
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(42)	(53)
Fair Value	1,434	$ 1,435
Commercial paper
Schedule of Investments [Line Items]
Amortized Cost	243
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	243
Certificates of deposit
Schedule of Investments [Line Items]
Amortized Cost	115
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	$ 115