Goodwill and Purchased Intangible Assets (Schedule of Intangible Assets Acquired Through Business Combinations) (Details) $ in Millions	12 Months Ended
	Jul. 29, 2017 USD ($) acquisition	Jul. 30, 2016 USD ($) acquisition	Jul. 25, 2015 USD ($) acquisition
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill	$ 878	$ 940	$ 99
Number of business combinations (acquisition) | acquisition	7
IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired	$ 0	223
TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite lived intangible assets acquired	614	544
CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite lived intangible assets acquired	238	142
OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite lived intangible assets acquired	26	31
CloudLock
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill	36
CloudLock | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired	$ 0
CloudLock | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	6 years
Finite lived intangible assets acquired	$ 32
CloudLock | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	4 years
Finite lived intangible assets acquired	$ 3
CloudLock | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	1 year 6 months
Finite lived intangible assets acquired	$ 1
AppDynamics
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill	785
AppDynamics | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired	$ 0
AppDynamics | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	4 years
Finite lived intangible assets acquired	$ 525
AppDynamics | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	7 years
Finite lived intangible assets acquired	$ 235
AppDynamics | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	2 years 3 months 18 days
Finite lived intangible assets acquired	$ 25
MindMeld
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill	51
MindMeld | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired	$ 0
MindMeld | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	4 years
Finite lived intangible assets acquired	$ 51
MindMeld | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	1 year
Finite lived intangible assets acquired	$ 0
MindMeld | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	0 years
Finite lived intangible assets acquired	$ 0
MaintenanceNet
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill		65
MaintenanceNet | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired		$ 11
MaintenanceNet | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		5 years
Finite lived intangible assets acquired		$ 50
MaintenanceNet | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		5 years
Finite lived intangible assets acquired		$ 2
MaintenanceNet | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		2 years
Finite lived intangible assets acquired		$ 2
OpenDNS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill		61
OpenDNS | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired		$ 1
OpenDNS | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		5 years
Finite lived intangible assets acquired		$ 43
OpenDNS | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		7 years
Finite lived intangible assets acquired		$ 15
OpenDNS | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		1 year
Finite lived intangible assets acquired		$ 2
Lancope
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill		121
Lancope | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired		$ 10
Lancope | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		5 years
Finite lived intangible assets acquired		$ 79
Lancope | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		6 years
Finite lived intangible assets acquired		$ 29
Lancope | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		3 years
Finite lived intangible assets acquired		$ 3
Acano
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill		103
Acano | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired		$ 82
Acano | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		5 years
Finite lived intangible assets acquired		$ 9
Acano | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		5 years
Finite lived intangible assets acquired		$ 12
Acano | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		0 years
Finite lived intangible assets acquired		$ 0
Leaba
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill		96
Leaba | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired		$ 96
Leaba | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		0 years
Finite lived intangible assets acquired		$ 0
Leaba | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		0 years
Finite lived intangible assets acquired		$ 0
Leaba | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		0 years
Finite lived intangible assets acquired		$ 0
Jasper
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill		361
Jasper | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired		$ 23
Jasper | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		6 years
Finite lived intangible assets acquired		$ 240
Jasper | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		7 years
Finite lived intangible assets acquired		$ 75
Jasper | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		2 years
Finite lived intangible assets acquired		$ 23
CliQr
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill		69
CliQr | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired		$ 0
CliQr | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		6 years
Finite lived intangible assets acquired		$ 65
CliQr | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		6 years
Finite lived intangible assets acquired		$ 3
CliQr | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		2 years
Finite lived intangible assets acquired		$ 1
Others
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite and indefinite-lived intangible assets acquired (excluding goodwill	$ 6	$ 64	$ 70
Number of business combinations (acquisition) | acquisition	4	5	5
Others | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired	$ 0	$ 0
Others | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	3 years	4 years 1 month 6 days
Finite lived intangible assets acquired	$ 6	$ 58
Others | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	0 years	6 years 3 months 18 days
Finite lived intangible assets acquired	$ 0	$ 6
Others | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	0 years	0 years
Finite lived intangible assets acquired	$ 0	$ 0