Goodwill and Purchased Intangible Assets (Schedule Of Intangible Assets Acquired Through Business Combinations) (Details) $ in Millions	6 Months Ended
	Jan. 23, 2016 USD ($)
Intangible Assets Acquired Through Business Combinations
Amount	$ 309
MaintenanceNet
Intangible Assets Acquired Through Business Combinations
Amount	65
OpenDNS
Intangible Assets Acquired Through Business Combinations
Amount	61
Lancope
Intangible Assets Acquired Through Business Combinations
Amount	121
Others (four in total)
Intangible Assets Acquired Through Business Combinations
Amount	62
Total
Intangible Assets Acquired Through Business Combinations
Amount	309
IPR&D
Intangible Assets Acquired Through Business Combinations
Amount	22
IPR&D | MaintenanceNet
Intangible Assets Acquired Through Business Combinations
Amount	11
IPR&D | OpenDNS
Intangible Assets Acquired Through Business Combinations
Amount	1
IPR&D | Lancope
Intangible Assets Acquired Through Business Combinations
Amount	10
IPR&D | Others (four in total)
Intangible Assets Acquired Through Business Combinations
Amount	0
TECHNOLOGY
Intangible Assets Acquired Through Business Combinations
Amount	$ 228
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 | Lancope
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	5 years
Amount	$ 79
TECHNOLOGY | Others (four in total)
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	4 years 2 months 12 days
Amount	$ 56
CUSTOMER RELATIONSHIPS
Intangible Assets Acquired Through Business Combinations
Amount	$ 52
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 | Lancope
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	6 years
Amount	$ 29
CUSTOMER RELATIONSHIPS | Others (four in total)
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	6 years 3 months 18 days
Amount	$ 6
OTHER
Intangible Assets Acquired Through Business Combinations
Amount	$ 7
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 | Lancope
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	3 years
Amount	$ 3
OTHER | Others (four in total)
Intangible Assets Acquired Through Business Combinations
Weighted- Average Useful Life (in Years)	0 years
Amount	$ 0