Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 25, 2014	Jul. 26, 2014
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	$ 2,622	$ 10,044
Gross unrealized losses, less than 12 months	(19)	(26)
Fair value of investment securities with unrealized losses12 months or greater	384	558
Gross unrealized losses, 12 months or greater	(2)	(4)
Fair value of investment securities with unrealized losses	3,006	10,602
Total gross unrealized losses	(21)	(30)
Publicly traded equity securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	131	132
Gross unrealized losses, less than 12 months	(11)	(10)
Fair value of investment securities with unrealized losses12 months or greater	1	0
Gross unrealized losses, 12 months or greater	0	0
Fair value of investment securities with unrealized losses	132	132
Total gross unrealized losses	(11)	(10)
Total fixed income securities
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	2,491	9,912
Gross unrealized losses, less than 12 months	(8)	(16)
Fair value of investment securities with unrealized losses12 months or greater	383	558
Gross unrealized losses, 12 months or greater	(2)	(4)
Fair value of investment securities with unrealized losses	2,874	10,470
Total gross unrealized losses	(10)	(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		7,676
Gross unrealized losses, less than 12 months		(12)
Fair value of investment securities with unrealized losses12 months or greater		45
Gross unrealized losses, 12 months or greater		0
Fair value of investment securities with unrealized losses		7,721
Total gross unrealized losses		(12)
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		361
Gross unrealized losses, less than 12 months		(1)
Fair value of investment securities with unrealized losses12 months or greater		22
Gross unrealized losses, 12 months or greater		0
Fair value of investment securities with unrealized losses		383
Total gross unrealized losses		(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	2,491	1,875
Gross unrealized losses, less than 12 months	(8)	(3)
Fair value of investment securities with unrealized losses12 months or greater	383	491
Gross unrealized losses, 12 months or greater	(2)	(4)
Fair value of investment securities with unrealized losses	2,874	2,366
Total gross unrealized losses	$ (10)	$ (7)