Goodwill and Purchased Intangible Assets (Schedule Of Intangible Assets Acquired Through Business Combinations) (Details) $ in Millions	3 Months Ended
	Oct. 24, 2015 USD ($)
Intangible Assets Acquired Through Business Combinations
Amount	$ 130
MaintenanceNet
Intangible Assets Acquired Through Business Combinations
Amount	65
OpenDNS
Intangible Assets Acquired Through Business Combinations
Amount	61
Other
Intangible Assets Acquired Through Business Combinations
Amount	4
Total
Intangible Assets Acquired Through Business Combinations
Amount	130
IPR&D
Intangible Assets Acquired Through Business Combinations
Amount	12
IPR&D | MaintenanceNet
Intangible Assets Acquired Through Business Combinations
Amount	11
IPR&D | OpenDNS
Intangible Assets Acquired Through Business Combinations
Amount	1
IPR&D | Other
Intangible Assets Acquired Through Business Combinations
Amount	0
TECHNOLOGY
Intangible Assets Acquired Through Business Combinations
Amount	$ 97
TECHNOLOGY | MaintenanceNet
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	5 years
Amount	$ 50
TECHNOLOGY | OpenDNS
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	5 years
Amount	$ 43
TECHNOLOGY | Other
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	5 years
Amount	$ 4
CUSTOMER RELATIONSHIPS
Intangible Assets Acquired Through Business Combinations
Amount	$ 17
CUSTOMER RELATIONSHIPS | MaintenanceNet
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	5 years
Amount	$ 2
CUSTOMER RELATIONSHIPS | OpenDNS
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	7 years
Amount	$ 15
CUSTOMER RELATIONSHIPS | Other
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	0 years
Amount	$ 0
OTHER | MaintenanceNet
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	2 years
Amount	$ 2
OTHER | OpenDNS
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	1 year
Amount	$ 2
OTHER | Other
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	0 years
Amount	$ 0