Goodwill And Purchased Intangible Assets (Schedule Of Intangible Assets Acquired Through Business Combinations) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jan. 25, 2014
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, total acquired Intangible Assets	$ 763
Compostie Software Inc. [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, total acquired Intangible Assets	75
Sourcefire Inc [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, total acquired Intangible Assets	577
WhipTail Technologies, Inc.
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, total acquired Intangible Assets	105
Other Acquisition [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, total acquired Intangible Assets	6
In Process Research and Development [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired indefinite lives	61
In Process Research and Development [Member] | Compostie Software Inc. [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired indefinite lives	1
In Process Research and Development [Member] | Sourcefire Inc [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired indefinite lives	22
In Process Research and Development [Member] | WhipTail Technologies, Inc.
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired indefinite lives	38
In Process Research and Development [Member] | Other Acquisition [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired indefinite lives	0
Technology [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired finite-lived	529
Technology [Member] | Compostie Software Inc. [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
Technology [Member] | Sourcefire Inc [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
Technology [Member] | WhipTail Technologies, Inc.
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	63
Technology [Member] | Other Acquisition [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	6
Customer Relationships [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired finite-lived	144
Customer Relationships [Member] | Compostie Software Inc. [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
Customer Relationships [Member] | Sourcefire Inc [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
Customer Relationships [Member] | WhipTail Technologies, Inc.
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	1
Customer Relationships [Member] | Other Acquisition [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
Other Intangible Assets [Member]
Schedule Of Finite Lived And Indefinite Lived Intangible Assets Acquired Through Business Combinations [Line Items]
Amount, acquired finite-lived	29
Other Intangible Assets [Member] | Compostie Software Inc. [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
Other Intangible Assets [Member] | Sourcefire Inc [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
Other Intangible Assets [Member] | WhipTail Technologies, Inc.
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, acquired finite-lived	3
Other Intangible Assets [Member] | Other Acquisition [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