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

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Amount before accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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