Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Apr. 30, 2022	May 01, 2021	Apr. 30, 2022	May 01, 2021
Disaggregation of Revenue [Line Items]
Revenue	$ 12,835	$ 12,803	$ 38,455	$ 36,692
Product
Disaggregation of Revenue [Line Items]
Revenue	9,448	9,139	28,330	26,298
Secure, Agile Networks
Disaggregation of Revenue [Line Items]
Revenue	5,869	5,620	17,735	16,543
Internet for the Future
Disaggregation of Revenue [Line Items]
Revenue	1,324	1,249	4,021	3,121
Collaboration
Disaggregation of Revenue [Line Items]
Revenue	1,132	1,220	3,308	3,580
End-to-End Security
Disaggregation of Revenue [Line Items]
Revenue	938	876	2,716	2,559
Optimized Application Experiences
Disaggregation of Revenue [Line Items]
Revenue	183	170	544	483
Other Products
Disaggregation of Revenue [Line Items]
Revenue	2	5	7	11
Services
Disaggregation of Revenue [Line Items]
Revenue	$ 3,387	$ 3,664	$ 10,125	$ 10,394