Segment Information and Major Customers - Summary of Net Revenue for Groups of Similar Products and Services (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 25, 2020	Jan. 26, 2019	Jan. 25, 2020	Jan. 26, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total	$ 12,005	$ 12,446	$ 25,164	$ 25,518
Discontinued operations, held-for-sale | Service Provider Video
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total				168
Total Product
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total	8,671	9,273	18,549	19,163
Infrastructure Platforms
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total	6,528	7,102	14,067	14,724
Applications
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total	1,349	1,465	2,847	2,884
Security
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total	748	684	1,563	1,354
Other Products
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total	46	22	72	200
Other Products | Discontinued operations, held-for-sale | Service Provider Video
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total				168
Service
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue, total	$ 3,334	$ 3,173	$ 6,615	$ 6,355