Available-for-Sale Debt Investments and Equity Investments - Summary of Gains and Losses Recognized on Marketable and Non-marketable Equity Securities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 25, 2020	Jan. 26, 2019	Jan. 25, 2020	Jan. 26, 2019
Investments, Debt and Equity Securities [Abstract]
Net gains and losses recognized during the period on equity investments	$ 71	$ 67	$ 78	$ 75
Less: Net gains and losses recognized on equity investments sold	(68)	5	(75)	(7)
Net unrealized gains and losses recognized during reporting period on equity securities still held at the reporting date	3	72	3	68
Adjustments to non-marketable equity securities measured using the measurement alternative:
Upward adjustments	11	14	12	24
Downward adjustments, including impairments	(8)	(2)	(9)	(18)
Net adjustments	$ 3	$ 12	$ 3	$ 6