Business Combinations (Summary Of Allocation Of Total Purchase Consideration) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jul. 26, 2014	Jul. 27, 2013	Jul. 28, 2012
Business Acquisition [Line Items]
Purchase Consideration	$ 3,181	$ 6,982
Net Tangible Assets Acquired (Liabilities Assumed)	25	(322)
Purchased Intangible Assets	838	2,391
Goodwill	2,318	4,913
Composite Software, Inc.
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 Technologies, Inc.
Business Acquisition [Line Items]
Purchase Consideration	351
Net Tangible Assets Acquired (Liabilities Assumed)	(34)
Purchased Intangible Assets	105
Goodwill	280
Tail-f Systems
Business Acquisition [Line Items]
Purchase Consideration	167
Net Tangible Assets Acquired (Liabilities Assumed)	(7)
Purchased Intangible Assets	61
Goodwill	113
NDS Group Limited
Business Acquisition [Line Items]
Purchase Consideration		5,005
Net Tangible Assets Acquired (Liabilities Assumed)		(185)
Purchased Intangible Assets		1,746
Goodwill		3,444
Meraki, Inc.
Business Acquisition [Line Items]
Purchase Consideration		974
Net Tangible Assets Acquired (Liabilities Assumed)		(59)
Purchased Intangible Assets		289
Goodwill		744
Intucell, Ltd.
Business Acquisition [Line Items]
Purchase Consideration		360
Net Tangible Assets Acquired (Liabilities Assumed)		(23)
Purchased Intangible Assets		106
Goodwill		277
Ubiquisys Limited
Business Acquisition [Line Items]
Purchase Consideration		280
Net Tangible Assets Acquired (Liabilities Assumed)		(30)
Purchased Intangible Assets		123
Goodwill		187
All others
Business Acquisition [Line Items]
Purchase Consideration	54	363	398
Net Tangible Assets Acquired (Liabilities Assumed)	(5)	(25)	(39)
Purchased Intangible Assets	20	127	200
Goodwill	$ 39	$ 261	$ 237