Available-for-Sale Debt and Equity Investments - Summary of Gains and Losses and Adjustments to the Carrying Value of Marketable and Non-marketable Equity Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 25, 2020	Jul. 27, 2019
Investments, Debt and Equity Securities [Abstract]
Net gains and losses recognized during the period on equity investments	$ 63	$ 58
Less: Net gains and losses recognized on equity investments sold	(76)	(69)
Net unrealized gains and losses recognized during reporting period on equity securities still held at the reporting date	(13)	(11)
Adjustments to non-marketable equity securities measured using the measurement alternative:
Upward adjustments	28	26
Downward adjustments, including impairments	(41)	(57)
Net adjustments	$ (13)	$ (31)