Available-for-Sale Debt Investments and Equity Investments (Available-for-Sale Investments With Gross Unrealized Losses) (Details) - USD ($) $ in Millions	Oct. 27, 2018	Jul. 28, 2018
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	$ 14,459	$ 21,093
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(272)	(391)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	13,496	9,019
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(267)	(156)
TOTAL, Fair Value	27,955	30,112
TOTAL, Gross Unrealized Losses	(539)	(547)
U.S. government securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	516	2,966
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(3)	(20)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	5,231	4,303
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(26)	(23)
TOTAL, Fair Value	5,747	7,269
TOTAL, Gross Unrealized Losses	(29)	(43)
U.S. government agency securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	4	206
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0	(2)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	427	521
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(4)	(3)
TOTAL, Fair Value	431	727
TOTAL, Gross Unrealized Losses	(4)	(5)
Non-U.S. government and agency securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	0	105
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	0	(1)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	153	103
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	0
TOTAL, Fair Value	153	208
TOTAL, Gross Unrealized Losses	0	(1)
Corporate debt securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	13,483	16,990
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(257)	(344)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	6,738	3,511
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(189)	(101)
TOTAL, Fair Value	20,221	20,501
TOTAL, Gross Unrealized Losses	(446)	(445)
U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	456	826
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(12)	(24)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	947	581
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(48)	(29)
TOTAL, Fair Value	1,403	1,407
TOTAL, Gross Unrealized Losses	$ (60)	$ (53)