Investments (Summary of Available-for-Sale Investments) (Details) - USD ($) $ in Millions	Jul. 29, 2017	Jul. 30, 2016
Available-for-sale investments: [Line Items]
Amortized Cost	$ 58,225	$ 57,479
Gross Unrealized Gains	762	703
Gross Unrealized Losses	(203)	(57)
Fair Value	58,784	58,125
Net unsettled available-for-sale investments, purchases	(30)	654
Total fixed income securities
Available-for-sale investments: [Line Items]
Amortized Cost	57,045	56,268
Gross Unrealized Gains	208	370
Gross Unrealized Losses	(176)	(17)
Fair Value	57,077	56,621
Total fixed income securities \| U.S. government securities
Available-for-sale investments: [Line Items]
Amortized Cost	19,880	26,473
Gross Unrealized Gains	3	73
Gross Unrealized Losses	(60)	(2)
Fair Value	19,823	26,544
Total fixed income securities \| U.S. government agency securities
Available-for-sale investments: [Line Items]
Amortized Cost	2,057	2,809
Gross Unrealized Gains	0	8
Gross Unrealized Losses	(5)	0
Fair Value	2,052	2,817
Total fixed income securities \| Non-U.S. government and agency securities
Available-for-sale investments: [Line Items]
Amortized Cost	389	1,096
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(1)	0
Fair Value	388	1,100
Total fixed income securities \| Corporate debt securities
Available-for-sale investments: [Line Items]
Amortized Cost	31,626	24,044
Gross Unrealized Gains	202	263
Gross Unrealized Losses	(93)	(15)
Fair Value	31,735	24,292
Total fixed income securities \| U.S. agency mortgage-backed securities
Available-for-sale investments: [Line Items]
Amortized Cost	2,037	1,846
Gross Unrealized Gains	3	22
Gross Unrealized Losses	(17)	0
Fair Value	2,023	1,868
Total fixed income securities \| Commercial paper
Available-for-sale investments: [Line Items]
Amortized Cost	996
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	996
Total fixed income securities \| Certificates of deposit
Available-for-sale investments: [Line Items]
Amortized Cost	60
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	60
Publicly traded equity securities
Available-for-sale investments: [Line Items]
Amortized Cost	1,180	1,211
Gross Unrealized Gains	554	333
Gross Unrealized Losses	(27)	(40)
Fair Value	$ 1,707	$ 1,504

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Net unsettled available-for-sale investments, purchases

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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