Investments (Summary Of Available-For-Sale Investments) (Details) - USD ($) $ in Millions	Oct. 29, 2016	Jul. 30, 2016
Schedule of Investments [Line Items]
Amortized Cost	$ 61,968	$ 57,479
Gross Unrealized Gains	568	703
Gross Unrealized Losses	(151)	(57)
Fair Value	62,385	58,125
Net unsettled available-for-sale investments, purchases	328	654
Total fixed income securities
Schedule of Investments [Line Items]
Amortized Cost	60,743	56,268
Gross Unrealized Gains	222	370
Gross Unrealized Losses	(97)	(17)
Fair Value	60,868	56,621
Total fixed income securities | U.S. government securities
Schedule of Investments [Line Items]
Amortized Cost	25,905	26,473
Gross Unrealized Gains	24	73
Gross Unrealized Losses	(33)	(2)
Fair Value	25,896	26,544
Total fixed income securities | U.S. government agency securities
Schedule of Investments [Line Items]
Amortized Cost	2,619	2,809
Gross Unrealized Gains	4	8
Gross Unrealized Losses	(1)	0
Fair Value	2,622	2,817
Total fixed income securities | Non-U.S. government and agency securities
Schedule of Investments [Line Items]
Amortized Cost	1,104	1,096
Gross Unrealized Gains	1	4
Gross Unrealized Losses	(1)	0
Fair Value	1,104	1,100
Total fixed income securities | Corporate debt securities
Schedule of Investments [Line Items]
Amortized Cost	29,046	24,044
Gross Unrealized Gains	177	263
Gross Unrealized Losses	(60)	(15)
Fair Value	29,163	24,292
Total fixed income securities | U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	2,069	1,846
Gross Unrealized Gains	16	22
Gross Unrealized Losses	(2)	0
Fair Value	2,083	1,868
Publicly traded equity securities
Schedule of Investments [Line Items]
Amortized Cost	1,225	1,211
Gross Unrealized Gains	346	333
Gross Unrealized Losses	(54)	(40)
Fair Value	$ 1,517	$ 1,504