Goodwill and Purchased Intangible Assets (Schedule Of Intangible Assets Acquired Through Business Combinations) (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 25, 2015	Jul. 26, 2014	Jul. 27, 2013
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	$ 99	$ 838	$ 2,391
IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	6	61
TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	72	596
CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	15	152
OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	6	29
Metacloud
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	29
Metacloud | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	$ 2
Metacloud | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	3 years
Amount	$ 24
Metacloud | 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
Amount	$ 3
Metacloud | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)
Amount	$ 0
Composite Software
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		75
Composite Software | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		$ 1
Composite Software | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		6 years
Amount		$ 60
Composite Software | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		3 years 10 months 8 days
Amount		$ 14
Composite Software | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)
Amount		$ 0
Sourcefire, Inc.
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		577
Sourcefire, Inc. | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		$ 22
Sourcefire, Inc. | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		7 years
Amount		$ 400
Sourcefire, Inc. | 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
Amount		$ 129
Sourcefire, Inc. | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		3 years
Amount		$ 26
WhipTail Technologies
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		105
WhipTail Technologies | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		$ 38
WhipTail Technologies | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		5 years
Amount		$ 63
WhipTail Technologies | 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
Amount		$ 1
WhipTail Technologies | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		2 years 8 months 12 days
Amount		$ 3
Tail-f
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		61
Tail-f | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		$ 0
Tail-f | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		7 years
Amount		$ 55
Tail-f | 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 9 months 18 days
Amount		$ 6
Tail-f | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)
Amount		$ 0
All others
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	70	20
All others | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	$ 4	$ 0
All 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 8 months 12 days	3 years 7 months 6 days
Amount	$ 48	$ 18
All others | CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	7 years 9 months 18 days	4 years
Amount	$ 12	$ 2
All others | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	5 years 9 months 18 days
Amount	$ 6	$ 0
Total
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	$ 99	$ 838