Fair Value - Fair Value, Nonrecurring Measurement (Details) - Level 3 - Fair value, measurements, nonrecurring - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 25, 2020	Jan. 26, 2019	Jan. 25, 2020	Jan. 26, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains (losses) for nonrecurring measurements	$ (14)	$ 12	$ (35)	$ 6
Non-marketable equity securities and equity method investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains (losses) for nonrecurring measurements	(11)	12	(32)	6
Purchased intangible assets (impaired)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains (losses) for nonrecurring measurements	$ (3)	$ 0	$ (3)	$ 0