Goodwill and Purchased Intangible Assets (Schedule Of Intangible Assets Acquired Through Business Combinations) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jul. 26, 2014	Jul. 27, 2013
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	$ 838	$ 2,391
IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	61	194
TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	596	1,286
CUSTOMER RELATIONSHIPS
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	152	883
OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	29	28
Composite Software, Inc.
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	75
Composite Software, Inc. | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	1
Composite Software, Inc. | 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, Inc. | 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, Inc. | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	0 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, Inc.
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	105
WhipTail Technologies, Inc. | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	38
WhipTail Technologies, Inc. | 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, 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	1
WhipTail Technologies, Inc. | 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 Systems
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	61
Tail-f Systems | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	0
Tail-f Systems | 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 Systems | 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 Systems | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	0 years
Amount	0
NDS Group Limited
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		1,746
NDS Group Limited | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		94
NDS Group Limited | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		6 years 4 months 24 days
Amount		807
NDS Group Limited | 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 8 months 4 days
Amount		818
NDS Group Limited | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		7 years 4 months 24 days
Amount		27
Meraki, Inc.
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		289
Meraki, Inc. | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		0
Meraki, Inc. | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		8 years
Amount		259
Meraki, Inc. | 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
Amount		30
Meraki, Inc. | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		0
Intucell, Ltd.
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		106
Intucell, Ltd. | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		36
Intucell, Ltd. | 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		59
Intucell, Ltd. | 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		11
Intucell, Ltd. | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		0
Ubiquisys Limited
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		123
Ubiquisys Limited | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		50
Ubiquisys Limited | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)		4 years
Amount		66
Ubiquisys Limited | 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		7
Ubiquisys Limited | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount		0
All others
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	20	127
All others | IPR&D
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	0	14
All others | TECHNOLOGY
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	3 years 7 months 6 days	4 years 8 months 12 days
Amount	18	95
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)	4 years	5 years 9 months 18 days
Amount	2	17
All others | OTHER
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted- Average Useful Life (in Years)	0 years	5 years
Amount	0	1
Total
Schedule of Finite Lived and Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount	$ 838	$ 2,391