Available-for-Sale Debt and Equity Investments - Available-for-Sale Investments With Gross Unrealized Losses (Details) - USD ($) $ in Millions	Jul. 25, 2020	Jul. 27, 2019
Schedule of Investments [Line Items]
Unrealized loss less than 12 months, Fair Value	$ 1,358	$ 2,689
Unrealized loss less than 12 months, Gross Unrealized Losses	(7)	(4)
Unrealized losses 12 months or greater, Fair Value	3	6,775
Unrealized losses 12 months or greater, Gross Unrealized Losses	0	(37)
Total, Fair Value	1,361	9,464
Total, Gross Unrealized Losses	(7)	(41)
U.S. government securities
Schedule of Investments [Line Items]
Unrealized loss less than 12 months, Fair Value		204
Unrealized loss less than 12 months, Gross Unrealized Losses		0
Unrealized losses 12 months or greater, Fair Value		488
Unrealized losses 12 months or greater, Gross Unrealized Losses		(1)
Total, Fair Value		692
Total, Gross Unrealized Losses		(1)
U.S. government agency securities
Schedule of Investments [Line Items]
Unrealized loss less than 12 months, Fair Value	33	0
Unrealized loss less than 12 months, Gross Unrealized Losses	0	0
Unrealized losses 12 months or greater, Fair Value	0	169
Unrealized losses 12 months or greater, Gross Unrealized Losses	0	0
Total, Fair Value	33	169
Total, Gross Unrealized Losses	0	0
Corporate debt securities
Schedule of Investments [Line Items]
Unrealized loss less than 12 months, Fair Value	1,060	2,362
Unrealized loss less than 12 months, Gross Unrealized Losses	(6)	(4)
Unrealized losses 12 months or greater, Fair Value	3	5,271
Unrealized losses 12 months or greater, Gross Unrealized Losses	0	(25)
Total, Fair Value	1,063	7,633
Total, Gross Unrealized Losses	(6)	(29)
U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
Unrealized loss less than 12 months, Fair Value	265	123
Unrealized loss less than 12 months, Gross Unrealized Losses	(1)	0
Unrealized losses 12 months or greater, Fair Value	0	847
Unrealized losses 12 months or greater, Gross Unrealized Losses	0	(11)
Total, Fair Value	265	970
Total, Gross Unrealized Losses	$ (1)	$ (11)