Investments (Summary Of Available-For-Sale Investments) (Details) - USD ($) $ in Millions	Jan. 28, 2017	Jul. 30, 2016
Schedule of Investments [Line Items]
Amortized Cost	$ 60,851	$ 57,479
Gross Unrealized Gains	555	703
Gross Unrealized Losses	(459)	(57)
Fair Value	60,947	58,125
Net unsettled available-for-sale investments, purchases	6	654
Total fixed income securities
Schedule of Investments [Line Items]
Amortized Cost	59,626	56,268
Gross Unrealized Gains	92	370
Gross Unrealized Losses	(385)	(17)
Fair Value	59,333	56,621
Total fixed income securities | U.S. government securities
Schedule of Investments [Line Items]
Amortized Cost	22,910	26,473
Gross Unrealized Gains	4	73
Gross Unrealized Losses	(82)	(2)
Fair Value	22,832	26,544
Total fixed income securities | U.S. government agency securities
Schedule of Investments [Line Items]
Amortized Cost	2,401	2,809
Gross Unrealized Gains	1	8
Gross Unrealized Losses	(5)	0
Fair Value	2,397	2,817
Total fixed income securities | Non-U.S. government and agency securities
Schedule of Investments [Line Items]
Amortized Cost	1,211	1,096
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(6)	0
Fair Value	1,205	1,100
Total fixed income securities | Corporate debt securities
Schedule of Investments [Line Items]
Amortized Cost	30,878	24,044
Gross Unrealized Gains	85	263
Gross Unrealized Losses	(265)	(15)
Fair Value	30,698	24,292
Total fixed income securities | U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	2,031	1,846
Gross Unrealized Gains	2	22
Gross Unrealized Losses	(27)	0
Fair Value	2,006	1,868
Total fixed income securities | Commercial paper
Schedule of Investments [Line Items]
Amortized Cost	195
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	195
Publicly traded equity securities
Schedule of Investments [Line Items]
Amortized Cost	1,225	1,211
Gross Unrealized Gains	463	333
Gross Unrealized Losses	(74)	(40)
Fair Value	$ 1,614	$ 1,504