Available-for-Sale Debt Investments and Equity Investments - Summary of Available-for-Sale Investments (Details) - USD ($) $ in Millions	Jan. 25, 2020	Jul. 27, 2019
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 18,371	$ 21,590
Gross Unrealized Gains	223	111
Gross Unrealized Losses	(7)	(41)
Fair Value	18,587	21,660
Net unsettled investment sales	13
U.S. government securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	2,218	808
Gross Unrealized Gains	13	1
Gross Unrealized Losses	0	(1)
Fair Value	2,231	808
U.S. government agency securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	20	169
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	20	169
Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	13,405	19,188
Gross Unrealized Gains	196	103
Gross Unrealized Losses	(4)	(29)
Fair Value	13,597	19,262
U.S. agency mortgage-backed securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	1,612	1,425
Gross Unrealized Gains	14	7
Gross Unrealized Losses	(3)	(11)
Fair Value	1,623	$ 1,421
Commercial paper
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	1,052
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	1,052
Certificates of deposit
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	64
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	$ 64

Debt Securities, Available-for-sale, Unsettled Sales, Net

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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