Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) - USD ($) $ in Millions	Oct. 29, 2016	Jul. 30, 2016
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	$ 22,758	$ 5,480
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(147)	(49)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	675	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(4)	(8)
TOTAL, Fair Value	23,433	6,688
TOTAL, Gross Unrealized Losses	(151)	(57)
Publicly traded equity securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	291	188
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(53)	(40)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	3	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(1)	0
TOTAL, Fair Value	294	188
TOTAL, Gross Unrealized Losses	(54)	(40)
Total fixed income securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	22,467	5,292
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(94)	(9)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	672	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(3)	(8)
TOTAL, Fair Value	23,139	6,500
TOTAL, Gross Unrealized Losses	(97)	(17)
Total fixed income securities | U.S. government securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	11,766	2,414
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(33)	(2)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	100	0
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	0	0
TOTAL, Fair Value	11,866	2,414
TOTAL, Gross Unrealized Losses	(33)	(2)
Total fixed income securities | U.S. government agency securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	596	144
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	596	144
TOTAL, Gross Unrealized Losses	(1)	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	498	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	498	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	9,013	2,499
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(57)	(7)
UNREALIZED LOSSES 12 MONTHS OR GREATER, Fair Value	572	1,208
UNREALIZED LOSSES 12 MONTHS OR GREATER, Gross Unrealized Losses	(3)	(8)
TOTAL, Fair Value	9,585	3,707
TOTAL, Gross Unrealized Losses	(60)	(15)
Total fixed income securities | U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
UNREALIZED LOSSES LESS THAN 12 MONTHS, Fair Value	594	174
UNREALIZED LOSSES LESS THAN 12 MONTHS, Gross Unrealized Losses	(2)	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	594	174
TOTAL, Gross Unrealized Losses	$ (2)	$ 0