Business Combinations (Summary Of Allocation Of Total Purchase Consideration) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 26, 2013
Business Acquisition [Line Items]
Total purchase consideration	$ 2,609
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	71
Amount, total acquired Intangible Assets	652
Goodwill	1,886
Sourcefire Inc [Member]
Business Acquisition [Line Items]
Total purchase consideration	2,449
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	81
Amount, total acquired Intangible Assets	577
Goodwill	1,791
Compostie Software Inc. [Member]
Business Acquisition [Line Items]
Total purchase consideration	160
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	(10)
Amount, total acquired Intangible Assets	75
Goodwill	$ 95