Goodwill and Purchased Intangible Assets - Schedule of Intangible Assets Acquired Through Business Combinations (Details) $ in Millions	12 Months Ended
	Jul. 27, 2019 USD ($) acquisition	Jul. 28, 2018 USD ($) acquisition	Jul. 29, 2017 acquisition
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Number of business combinations (acquisition) | acquisition	5		7
Purchased Intangible Assets	$ 672	$ 867
IPR&D
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired	333	3
TECHNOLOGY
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite lived intangible assets acquired	166	650
CUSTOMER RELATIONSHIPS
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite lived intangible assets acquired	152	207
OTHER
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Finite lived intangible assets acquired	21	$ 7
Duo
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Purchased Intangible Assets	342
Duo | IPR&D
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired	$ 77
Duo | 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	$ 153
Duo | 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	$ 94
Duo | OTHER
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	2 years 6 months
Finite lived intangible assets acquired	$ 18
Luxtera
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Purchased Intangible Assets	319
Luxtera | IPR&D
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired	$ 256
Luxtera | 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	$ 2
Luxtera | 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	$ 58
Luxtera | OTHER
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	1 year 7 months 6 days
Finite lived intangible assets acquired	$ 3
Others
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Number of business combinations (acquisition) | acquisition	3	4
Purchased Intangible Assets	$ 11	$ 42
Others | TECHNOLOGY
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	4 years 4 months 24 days	3 years 10 months 24 days
Finite lived intangible assets acquired	$ 11	$ 39
Others | 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
Viptela
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Purchased Intangible Assets		$ 180
Viptela | 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		$ 144
Viptela | 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		$ 35
Viptela | 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		$ 1
Springpath
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Purchased Intangible Assets		160
Springpath | IPR&D
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Indefinite-lived intangible assets acquired		$ 3
Springpath | 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		$ 157
BroadSoft
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Purchased Intangible Assets		$ 430
BroadSoft | 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		$ 255
BroadSoft | 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		$ 169
BroadSoft | 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		$ 6
Accompany
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Purchased Intangible Assets		$ 55
Accompany | 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		$ 55