Goodwill and Purchased Intangible Assets (Schedule of Intangible Assets Acquired Through Business Combinations) (Details) $ in Millions	6 Months Ended
	Jan. 27, 2018 USD ($) acquisition
Intangible Assets Acquired Through Business Combinations
Total, Amount	$ 361
Number of business combinations (acquisition) | acquisition	5
Viptela
Intangible Assets Acquired Through Business Combinations
Total, Amount	$ 180
Springpath
Intangible Assets Acquired Through Business Combinations
Total, Amount	160
Others (three in total)
Intangible Assets Acquired Through Business Combinations
Total, Amount	$ 21
Number of business combinations (acquisition) | acquisition	3
IPR&D
Intangible Assets Acquired Through Business Combinations
Indefinite Lives, Amount	$ 3
IPR&D | Viptela
Intangible Assets Acquired Through Business Combinations
Indefinite Lives, Amount	0
IPR&D | Springpath
Intangible Assets Acquired Through Business Combinations
Indefinite Lives, Amount	3
IPR&D | Others (three in total)
Intangible Assets Acquired Through Business Combinations
Indefinite Lives, Amount	0
TECHNOLOGY
Intangible Assets Acquired Through Business Combinations
Finite Lives, Amount	$ 319
TECHNOLOGY | Viptela
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	5 years
Finite Lives, Amount	$ 144
TECHNOLOGY | Springpath
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	4 years
Finite Lives, Amount	$ 157
TECHNOLOGY | Others (three in total)
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	2 years 6 months
Finite Lives, Amount	$ 18
CUSTOMER RELATIONSHIPS
Intangible Assets Acquired Through Business Combinations
Finite Lives, Amount	$ 38
CUSTOMER RELATIONSHIPS | Viptela
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	6 years
Finite Lives, Amount	$ 35
CUSTOMER RELATIONSHIPS | Springpath
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	0 years
Finite Lives, Amount	$ 0
CUSTOMER RELATIONSHIPS | Others (three in total)
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	4 years
Finite Lives, Amount	$ 3
OTHER
Intangible Assets Acquired Through Business Combinations
Finite Lives, Amount	$ 1
OTHER | Viptela
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	1 year
Finite Lives, Amount	$ 1
OTHER | Springpath
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	0 years
Finite Lives, Amount	$ 0
OTHER | Others (three in total)
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	0 years
Finite Lives, Amount	$ 0