Available-for-Sale Debt Investments and Equity Investments - Available-for-Sale Investments With Gross Unrealized Losses (Details) - USD ($) $ in Millions	Jan. 25, 2020	Jul. 27, 2019
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	$ 447	$ 2,689
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(1)	(4)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	836	6,775
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(6)	(37)
TOTAL, Fair Value	1,283	9,464
TOTAL, Gross Unrealized Losses	(7)	(41)
U.S. government securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	44	204
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	20	488
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	(1)
TOTAL, Fair Value	64	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	0	0
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	3	169
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	0
TOTAL, Fair Value	3	169
TOTAL, Gross Unrealized Losses	0	0
Corporate debt securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	260	2,362
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(1)	(4)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	439	5,271
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(3)	(25)
TOTAL, Fair Value	699	7,633
TOTAL, Gross Unrealized Losses	(4)	(29)
U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	56	123
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	374	847
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(3)	(11)
TOTAL, Fair Value	430	970
TOTAL, Gross Unrealized Losses	(3)	$ (11)
Commercial paper
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	51
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	51
TOTAL, Gross Unrealized Losses	0
Certificates of deposit
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	36
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	36
TOTAL, Gross Unrealized Losses	$ 0