Available-for-Sale Debt and Equity Investments - Summary of Available-for-Sale Investments (Details) - USD ($) $ in Millions	Jul. 25, 2020	Jul. 27, 2019
Schedule of Investments [Line Items]
Amortized Cost	$ 17,163	$ 21,590
Gross Unrealized Gains	454	111
Gross Unrealized Losses	(7)	(41)
Available-for-sale debt investments	17,610	21,660
U.S. government securities
Schedule of Investments [Line Items]
Amortized Cost	2,614	808
Gross Unrealized Gains	71	1
Gross Unrealized Losses	0	(1)
Available-for-sale debt investments	2,685	808
U.S. government agency securities
Schedule of Investments [Line Items]
Amortized Cost	110	169
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Available-for-sale debt investments	110	169
Corporate debt securities
Schedule of Investments [Line Items]
Amortized Cost	11,549	19,188
Gross Unrealized Gains	334	103
Gross Unrealized Losses	(6)	(29)
Available-for-sale debt investments	11,877	19,262
U.S. agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	1,987	1,425
Gross Unrealized Gains	49	7
Gross Unrealized Losses	(1)	(11)
Available-for-sale debt investments	2,035	$ 1,421
Commercial paper
Schedule of Investments [Line Items]
Amortized Cost	727
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Available-for-sale debt investments	727
Certificates of deposit
Schedule of Investments [Line Items]
Amortized Cost	176
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Available-for-sale debt investments	$ 176

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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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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