Available-for-Sale Debt Investments and Equity Investments - Available-for-Sale Investments With Gross Unrealized Losses (Details) - USD ($) $ in Millions	Jul. 27, 2019	Jul. 28, 2018
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Unrealized loss less than 12 months, Fair Value	$ 2,689	$ 21,093
Unrealized loss less than 12 months, Gross Unrealized Losses	(4)	(391)
Unrealized losses 12 months or greater, Fair Value	6,775	9,019
Unrealized losses 12 months or greater, Gross Unrealized Losses	(37)	(156)
Total, Fair Value	9,464	30,112
Total, Gross Unrealized Losses	(41)	(547)
U.S. government securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Unrealized loss less than 12 months, Fair Value	204	2,966
Unrealized loss less than 12 months, Gross Unrealized Losses	0	(20)
Unrealized losses 12 months or greater, Fair Value	488	4,303
Unrealized losses 12 months or greater, Gross Unrealized Losses	(1)	(23)
Total, Fair Value	692	7,269
Total, Gross Unrealized Losses	(1)	(43)
U.S. government agency securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Unrealized loss less than 12 months, Fair Value	0	206
Unrealized loss less than 12 months, Gross Unrealized Losses	0	(2)
Unrealized losses 12 months or greater, Fair Value	169	521
Unrealized losses 12 months or greater, Gross Unrealized Losses	0	(3)
Total, Fair Value	169	727
Total, Gross Unrealized Losses	0	(5)
Non-U.S. government and agency securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Unrealized loss less than 12 months, Fair Value		105
Unrealized loss less than 12 months, Gross Unrealized Losses		(1)
Unrealized losses 12 months or greater, Fair Value		103
Unrealized losses 12 months or greater, Gross Unrealized Losses		0
Total, Fair Value		208
Total, Gross Unrealized Losses		(1)
Corporate debt securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Unrealized loss less than 12 months, Fair Value	2,362	16,990
Unrealized loss less than 12 months, Gross Unrealized Losses	(4)	(344)
Unrealized losses 12 months or greater, Fair Value	5,271	3,511
Unrealized losses 12 months or greater, Gross Unrealized Losses	(25)	(101)
Total, Fair Value	7,633	20,501
Total, Gross Unrealized Losses	(29)	(445)
U.S. agency mortgage-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Unrealized loss less than 12 months, Fair Value	123	826
Unrealized loss less than 12 months, Gross Unrealized Losses	0	(24)
Unrealized losses 12 months or greater, Fair Value	847	581
Unrealized losses 12 months or greater, Gross Unrealized Losses	(11)	(29)
Total, Fair Value	970	1,407
Total, Gross Unrealized Losses	$ (11)	$ (53)