Goodwill And Purchased Intangible Assets (Schedule Of Intangible Assets Acquired Through Business Combinations) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 26, 2013
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired indefinite lives	$ 23
Amount, total acquired Intangible Assets	652
Technology [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired finite-lived	460
Customer Relationships [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired finite-lived	143
Other Intangible Assets [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired finite-lived	26
Sourcefire Inc [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired indefinite lives	22
Amount, total acquired Intangible Assets	577
Sourcefire Inc [Member] | Technology [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted-Average Useful Life (in Years)	7 years
Amount, acquired finite-lived	400
Sourcefire Inc [Member] | Customer Relationships [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted-Average Useful Life (in Years)	5 years
Amount, acquired finite-lived	129
Sourcefire Inc [Member] | Other Intangible Assets [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted-Average Useful Life (in Years)	3 years
Amount, acquired finite-lived	26
Compostie Software Inc. [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired indefinite lives	1
Amount, total acquired Intangible Assets	75
Compostie Software Inc. [Member] | Technology [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted-Average Useful Life (in Years)	6 years
Amount, acquired finite-lived	60
Compostie Software Inc. [Member] | Customer Relationships [Member]
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, acquired finite-lived	14
Compostie Software Inc. [Member] | Other Intangible Assets [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Weighted-Average Useful Life (in Years)	0 years
Amount, acquired finite-lived	$ 0