Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) - USD ($) $ in Millions	Jul. 29, 2017	Jul. 30, 2016
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	$ 28,215	$ 5,480
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(195)	(49)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	1,040	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(8)	(8)
TOTAL, Fair Value	29,255	6,688
TOTAL, Gross Unrealized Losses	(203)	(57)
Publicly traded equity securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	122	188
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(27)	(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	122	188
TOTAL, Gross Unrealized Losses	(27)	(40)
Total fixed income securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	28,093	5,292
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(168)	(9)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	1,040	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(8)	(8)
TOTAL, Fair Value	29,133	6,500
TOTAL, Gross Unrealized Losses	(176)	(17)
Total fixed income securities | U.S. government securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	14,962	2,414
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(55)	(2)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	771	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(5)	0
TOTAL, Fair Value	15,733	2,414
TOTAL, Gross Unrealized Losses	(60)	(2)
Total fixed income securities | U.S. government agency securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	1,791	144
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(4)	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	130	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(1)	0
TOTAL, Fair Value	1,921	144
TOTAL, Gross Unrealized Losses	(5)	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	368	61
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(1)	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	368	61
TOTAL, Gross Unrealized Losses	(1)	0
Total fixed income securities | Corporate debt securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	9,487	2,499
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(92)	(7)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	101	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(1)	(8)
TOTAL, Fair Value	9,588	3,707
TOTAL, Gross Unrealized Losses	(93)	(15)
Total fixed income securities | U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	1,485	174
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(16)	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	38	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(1)	0
TOTAL, Fair Value	1,523	174
TOTAL, Gross Unrealized Losses	$ (17)	$ 0