Goodwill and Purchased Intangible Assets (Schedule Of Intangible Assets Acquired Through Business Combinations) (Details) $ in Millions	3 Months Ended
	Oct. 28, 2017 USD ($)
Intangible Assets Acquired Through Business Combinations
Total, Amount	$ 346
Viptela
Intangible Assets Acquired Through Business Combinations
Total, Amount	180
Springpath
Intangible Assets Acquired Through Business Combinations
Total, Amount	160
Other
Intangible Assets Acquired Through Business Combinations
Total, Amount	6
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 | Other
Intangible Assets Acquired Through Business Combinations
Indefinite Lives, Amount	0
TECHNOLOGY
Intangible Assets Acquired Through Business Combinations
Finite Lives, Amount	$ 304
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 | Other
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	5 years
Finite Lives, Amount	$ 3
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 | Other
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 | Other
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	0 years
Finite Lives, Amount	$ 0