Investments (Summary of Available-for-Sale Investments) (Details) - USD ($) $ in Millions	Jul. 28, 2018	Jul. 29, 2017
Available-for-sale investments: [Line Items]
Amortized Cost	$ 37,884	$ 58,225
Gross Unrealized Gains	277	762
Gross Unrealized Losses	(547)	(203)
Fair Value	37,614	58,784
Fixed Income Investments
Available-for-sale investments: [Line Items]
Amortized Cost	37,512	57,045
Gross Unrealized Gains	44	208
Gross Unrealized Losses	(547)	(176)
Fair Value	37,009	57,077
Fixed Income Investments \| U.S. government securities
Available-for-sale investments: [Line Items]
Amortized Cost	7,318	19,880
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(43)	(60)
Fair Value	7,275	19,823
Fixed Income Investments \| U.S. government agency securities
Available-for-sale investments: [Line Items]
Amortized Cost	732	2,057
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(5)	(5)
Fair Value	727	2,052
Fixed Income Investments \| Non-U.S. government and agency securities
Available-for-sale investments: [Line Items]
Amortized Cost	209	389
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(1)
Fair Value	208	388
Fixed Income Investments \| Corporate debt securities
Available-for-sale investments: [Line Items]
Amortized Cost	27,765	31,626
Gross Unrealized Gains	44	202
Gross Unrealized Losses	(445)	(93)
Fair Value	27,364	31,735
Fixed Income Investments \| U.S. agency mortgage-backed securities
Available-for-sale investments: [Line Items]
Amortized Cost	1,488	2,037
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(53)	(17)
Fair Value	1,435	2,023
Fixed Income Investments \| Commercial paper
Available-for-sale investments: [Line Items]
Amortized Cost		996
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		996
Fixed Income Investments \| 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	372	1,180
Gross Unrealized Gains	233	554
Gross Unrealized Losses	0	(27)
Fair Value	$ 605	$ 1,707

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

+ References

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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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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