Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) - USD ($) $ in Millions	Apr. 29, 2017	Jul. 30, 2016
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	$ 33,231	$ 5,480
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(256)	(49)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	104	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(1)	(8)
TOTAL, Fair Value	33,335	6,688
TOTAL, Gross Unrealized Losses	(257)	(57)
Publicly traded equity securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	50	188
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(4)	(40)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	0	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	0
TOTAL, Fair Value	50	188
TOTAL, Gross Unrealized Losses	(4)	(40)
Total fixed income securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	33,181	5,292
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(252)	(9)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	104	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(1)	(8)
TOTAL, Fair Value	33,285	6,500
TOTAL, Gross Unrealized Losses	(253)	(17)
Total fixed income securities | U.S. government securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	17,231	2,414
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(67)	(2)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	16	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	0
TOTAL, Fair Value	17,247	2,414
TOTAL, Gross Unrealized Losses	(67)	(2)
Total fixed income securities | U.S. government agency securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	1,980	144
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(6)	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	0	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	0
TOTAL, Fair Value	1,980	144
TOTAL, Gross Unrealized Losses	(6)	0
Total fixed income securities | Non-U.S. government and agency securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	607	61
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(2)	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	6	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	0
TOTAL, Fair Value	613	61
TOTAL, Gross Unrealized Losses	(2)	0
Total fixed income securities | Corporate debt securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	11,915	2,499
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(159)	(7)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	78	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(1)	(8)
TOTAL, Fair Value	11,993	3,707
TOTAL, Gross Unrealized Losses	(160)	(15)
Total fixed income securities | U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	1,448	174
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(18)	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	4	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	0
TOTAL, Fair Value	1,452	174
TOTAL, Gross Unrealized Losses	$ (18)	$ 0