Available-for-Sale Debt Investments and Equity Investments - Available-for-Sale Investments With Gross Unrealized Losses (Details) - USD ($) $ in Millions	Apr. 25, 2020	Jul. 27, 2019
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	$ 4,607	$ 2,689
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(86)	(4)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	23	6,775
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	(37)
TOTAL, Fair Value	4,630	9,464
TOTAL, Gross Unrealized Losses	(86)	(41)
U.S. government securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	26	204
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	0	488
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	(1)
TOTAL, Fair Value	26	692
TOTAL, Gross Unrealized Losses	0	(1)
U.S. government agency securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	10	0
UNREALIZED LOSSES 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	10	169
TOTAL, Gross Unrealized Losses	0	0
Corporate debt securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	3,529	2,362
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(86)	(4)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	23	5,271
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	(25)
TOTAL, Fair Value	3,552	7,633
TOTAL, Gross Unrealized Losses	(86)	(29)
U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	19	123
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0	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	19	970
TOTAL, Gross Unrealized Losses	0	$ (11)
Commercial paper
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	1,013
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0
TOTAL, Fair Value	1,013
TOTAL, Gross Unrealized Losses	0
Certificates of deposit
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	10
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0
TOTAL, Fair Value	10
TOTAL, Gross Unrealized Losses	$ 0