Acquisitions and Divestitures (Summary Of Allocation Of Total Purchase Consideration) (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 30, 2016	Jul. 25, 2015	Jul. 26, 2014
Business Acquisition [Line Items]
Purchase Consideration	$ 3,378	$ 334	$ 3,181
Net Tangible Assets Acquired (Liabilities Assumed)	(124)	(20)	25
Purchased Intangible Assets	940	99	838
Goodwill	2,562	255	2,318
MaintenanceNet
Business Acquisition [Line Items]
Purchase Consideration	105
Net Tangible Assets Acquired (Liabilities Assumed)	(21)
Purchased Intangible Assets	65
Goodwill	61
OpenDNS
Business Acquisition [Line Items]
Purchase Consideration	545
Net Tangible Assets Acquired (Liabilities Assumed)	(9)
Purchased Intangible Assets	61
Goodwill	493
Lancope
Business Acquisition [Line Items]
Purchase Consideration	410
Net Tangible Assets Acquired (Liabilities Assumed)	(34)
Purchased Intangible Assets	121
Goodwill	323
Acano
Business Acquisition [Line Items]
Purchase Consideration	528
Net Tangible Assets Acquired (Liabilities Assumed)	(27)
Purchased Intangible Assets	103
Goodwill	452
Leaba
Business Acquisition [Line Items]
Purchase Consideration	219
Net Tangible Assets Acquired (Liabilities Assumed)	(18)
Purchased Intangible Assets	96
Goodwill	141
Jasper
Business Acquisition [Line Items]
Purchase Consideration	1,234
Net Tangible Assets Acquired (Liabilities Assumed)	5
Purchased Intangible Assets	361
Goodwill	868
Cliqr
Business Acquisition [Line Items]
Purchase Consideration	225
Net Tangible Assets Acquired (Liabilities Assumed)	(3)
Purchased Intangible Assets	69
Goodwill	159
Metacloud
Business Acquisition [Line Items]
Purchase Consideration		149
Net Tangible Assets Acquired (Liabilities Assumed)		(7)
Purchased Intangible Assets		29
Goodwill		127
Composite Software
Business Acquisition [Line Items]
Purchase Consideration			160
Net Tangible Assets Acquired (Liabilities Assumed)			(10)
Purchased Intangible Assets			75
Goodwill			95
Sourcefire, Inc.
Business Acquisition [Line Items]
Purchase Consideration			2,449
Net Tangible Assets Acquired (Liabilities Assumed)			81
Purchased Intangible Assets			577
Goodwill			1,791
WhipTail
Business Acquisition [Line Items]
Purchase Consideration			351
Net Tangible Assets Acquired (Liabilities Assumed)			(34)
Purchased Intangible Assets			105
Goodwill			280
Tail-f
Business Acquisition [Line Items]
Purchase Consideration			167
Net Tangible Assets Acquired (Liabilities Assumed)			(7)
Purchased Intangible Assets			61
Goodwill			113
All others
Business Acquisition [Line Items]
Purchase Consideration	112	185	54
Net Tangible Assets Acquired (Liabilities Assumed)	(17)	(13)	(5)
Purchased Intangible Assets	64	70	20
Goodwill	$ 65	$ 128	$ 39