Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 25, 2015	Jul. 26, 2014
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	$ 18,599	$ 10,044
Gross unrealized losses, less than 12 months	(67)	(26)
Fair value of investment securities with unrealized losses12 months or greater	318	558
Gross unrealized losses, 12 months or greater	(4)	(4)
Fair value of investment securities with unrealized losses	18,917	10,602
Total gross unrealized losses	(71)	(30)
Publicly traded equity securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	108	132
Gross unrealized losses, less than 12 months	(7)	(10)
Fair value of investment securities with unrealized losses12 months or greater	2	0
Gross unrealized losses, 12 months or greater	0	0
Fair value of investment securities with unrealized losses	110	132
Total gross unrealized losses	(7)	(10)
Total fixed income securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	18,491	9,912
Gross unrealized losses, less than 12 months	(60)	(16)
Fair value of investment securities with unrealized losses12 months or greater	316	558
Gross unrealized losses, 12 months or greater	(4)	(4)
Fair value of investment securities with unrealized losses	18,807	10,470
Total gross unrealized losses	(64)	(20)
Total fixed income securities | U.S. government securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	6,412	7,676
Gross unrealized losses, less than 12 months	(6)	(12)
Fair value of investment securities with unrealized losses12 months or greater	0	45
Gross unrealized losses, 12 months or greater	0	0
Fair value of investment securities with unrealized losses	6,412	7,721
Total gross unrealized losses	(6)	(12)
Total fixed income securities | U.S. government agency securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	1,433
Gross unrealized losses, less than 12 months	(1)
Fair value of investment securities with unrealized losses12 months or greater	0
Gross unrealized losses, 12 months or greater	0
Fair value of investment securities with unrealized losses	1,433
Total gross unrealized losses	(1)
Total fixed income securities | Non-U.S. government and agency securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	515	361
Gross unrealized losses, less than 12 months	(1)	(1)
Fair value of investment securities with unrealized losses12 months or greater	4	22
Gross unrealized losses, 12 months or greater	0	0
Fair value of investment securities with unrealized losses	519	383
Total gross unrealized losses	(1)	(1)
Total fixed income securities | Corporate debt securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	9,552	1,875
Gross unrealized losses, less than 12 months	(49)	(3)
Fair value of investment securities with unrealized losses12 months or greater	312	491
Gross unrealized losses, 12 months or greater	(4)	(4)
Fair value of investment securities with unrealized losses	9,864	2,366
Total gross unrealized losses	(53)	$ (7)
Total fixed income securities | Asset-backed Securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	579
Gross unrealized losses, less than 12 months	(3)
Fair value of investment securities with unrealized losses12 months or greater	0
Gross unrealized losses, 12 months or greater	0
Fair value of investment securities with unrealized losses	579
Total gross unrealized losses	$ (3)