Investments (Available-For-Sale Investments With Gross Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified	Apr. 28, 2012	Jul. 30, 2011
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	$ 8,516	$ 3,845
Gross unrealized losses, less than 12 months	(12)	(16)
Fair value of investment securities with unrealized losses12 months or greater	36	161
Gross unrealized losses, 12 months or greater	(2)	(6)
Fair value of investment securities with unrealized losses	8,552	4,006
Total gross unrealized losses	(14)	(22)
Publicly Traded Equity Securities [Member]
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	42	112
Gross unrealized losses, less than 12 months	(4)	(12)
Fair value of investment securities with unrealized losses12 months or greater	1
Fair value of investment securities with unrealized losses	43	112
Total gross unrealized losses	(4)	(12)
Total Fixed Income Securities [Member]
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	8,474	3,733
Gross unrealized losses, less than 12 months	(8)	(4)
Fair value of investment securities with unrealized losses12 months or greater	35	161
Gross unrealized losses, 12 months or greater	(2)	(6)
Fair value of investment securities with unrealized losses	8,509	3,894
Total gross unrealized losses	(10)	(10)
Total Fixed Income Securities [Member] | U.S. Government Agency Securities [Member]
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months		2,310
Gross unrealized losses, less than 12 months		(1)
Fair value of investment securities with unrealized losses		2,310
Total gross unrealized losses		(1)
Total Fixed Income Securities [Member] | Non-U.S. Government And Agency Securities [Member]
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	6,756	875
Gross unrealized losses, less than 12 months	(2)	(1)
Fair value of investment securities with unrealized losses	6,756	875
Total gross unrealized losses	(2)	(1)
Total Fixed Income Securities [Member] | Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses less than 12 months	1,718	548
Gross unrealized losses, less than 12 months	(6)	(2)
Fair value of investment securities with unrealized losses12 months or greater	21	56
Gross unrealized losses, 12 months or greater		(2)
Fair value of investment securities with unrealized losses	1,739	604
Total gross unrealized losses	(6)	(4)
Total Fixed Income Securities [Member] | Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Fair value of investment securities with unrealized losses12 months or greater	14	105
Gross unrealized losses, 12 months or greater	(2)	(4)
Fair value of investment securities with unrealized losses	14	105
Total gross unrealized losses	$ (2)	$ (4)