Business Combinations (Summary Of Allocation Of Total Purchase Consideration) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jan. 25, 2014
Business Acquisition [Line Items]
Total purchase consideration	$ 2,970
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	35
Amount, total acquired Intangible Assets	763
Goodwill, Gross	2,172
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, Gross	95
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, Gross	1,791
WhipTail Technologies, Inc.
Business Acquisition [Line Items]
Total purchase consideration	351
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	(34)
Amount, total acquired Intangible Assets	105
Goodwill, Gross	280
Other Acquisition [Member]
Business Acquisition [Line Items]
Total purchase consideration	10
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	(2)
Amount, total acquired Intangible Assets	6
Goodwill, Gross	$ 6