Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jul. 27, 2019	Apr. 27, 2019	Jan. 26, 2019	Oct. 27, 2018	Jul. 28, 2018	Apr. 28, 2018	Jan. 27, 2018	Oct. 28, 2017	Jul. 27, 2019	Jul. 28, 2018	Jul. 29, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 13,428	$ 12,958	$ 12,446	$ 13,072	$ 12,844	$ 12,463	$ 11,887	$ 12,136	$ 51,904	$ 49,330	$ 48,005
Product
Disaggregation of Revenue [Line Items]
Revenue									39,005	36,709	35,705
Infrastructure Platforms
Disaggregation of Revenue [Line Items]
Revenue									30,191	28,322	27,817
Applications
Disaggregation of Revenue [Line Items]
Revenue									5,803	5,036	4,568
Security
Disaggregation of Revenue [Line Items]
Revenue									2,730	2,352	2,152
Other Products
Disaggregation of Revenue [Line Items]
Revenue									281	999	1,168
Other Products | Discontinued operations, held-for-sale | Service Provider Video
Disaggregation of Revenue [Line Items]
Revenue									168	903
Service
Disaggregation of Revenue [Line Items]
Revenue									$ 12,899	$ 12,621	$ 12,300