Acquisitions and Divestitures (Summary of Allocation of Total Purchase Consideration) (Details) $ in Millions	12 Months Ended
	Jul. 29, 2017 USD ($) acquisition	Jul. 30, 2016 USD ($) acquisition	Jul. 25, 2015 USD ($) acquisition
Business Acquisition [Line Items]
Purchase Consideration	$ 3,637	$ 3,378	$ 334
Net Tangible Assets Acquired (Liabilities Assumed)	(186)	(124)	(20)
Purchased Intangible Assets	878	940	99
Goodwill	$ 2,945	2,562	255
Number of business combinations (acquisition) | acquisition	7
CloudLock
Business Acquisition [Line Items]
Purchase Consideration	$ 249
Net Tangible Assets Acquired (Liabilities Assumed)	0
Purchased Intangible Assets	36
Goodwill	213
AppDynamics
Business Acquisition [Line Items]
Purchase Consideration	3,258
Net Tangible Assets Acquired (Liabilities Assumed)	(175)
Purchased Intangible Assets	785
Goodwill	2,648
MindMeld
Business Acquisition [Line Items]
Purchase Consideration	104
Net Tangible Assets Acquired (Liabilities Assumed)	(11)
Purchased Intangible Assets	51
Goodwill	64
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
Others
Business Acquisition [Line Items]
Purchase Consideration	26	112	185
Net Tangible Assets Acquired (Liabilities Assumed)	0	(17)	(13)
Purchased Intangible Assets	6	64	70
Goodwill	$ 20	$ 65	$ 128
Number of business combinations (acquisition) | acquisition	4	5	5