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
	Oct. 26, 2019	Oct. 27, 2018
Adjustments to non-marketable equity securities measured using the measurement alternative:
Upward adjustments	$ 1	$ 10
Downward adjustments, including impairments	(2)	(16)
Net adjustments	(1)	(6)
Net gains and losses recognized during the period on equity investments	7	8
Less: Net gains and losses recognized on equity investments sold	(8)	(12)
Net unrealized gains and losses recognized during reporting period on equity securities still held at the reporting date	$ (1)	$ (4)