Acquisitions and Divestitures (Additional Information Acquisitions) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Apr. 30, 2016	Apr. 30, 2016 USD ($) acquisitions	Apr. 25, 2015 USD ($)
Supplementary Information [Line Items]
Number of business combinations (in numbers) | acquisitions		12
Acquired Cash and Cash Equivalents		$ 44
Purchase Consideration		3,378
General and administrative
Supplementary Information [Line Items]
Business Combination, Acquisition Related Costs		29	$ 5
MaintenanceNet
Supplementary Information [Line Items]
Business Acquisition, Effective Date of Acquisition	Aug. 06, 2015
Purchase Consideration		105
OpenDNS
Supplementary Information [Line Items]
Business Acquisition, Effective Date of Acquisition	Aug. 26, 2015
Purchase Consideration		545
Lancope
Supplementary Information [Line Items]
Business Acquisition, Effective Date of Acquisition	Dec. 21, 2015
Purchase Consideration		410
Acano
Supplementary Information [Line Items]
Business Acquisition, Effective Date of Acquisition	Jan. 29, 2016
Purchase Consideration		528
Leaba
Supplementary Information [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 03, 2016
Purchase Consideration		219
Jasper
Supplementary Information [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 18, 2016
Purchase Consideration		1,234
CliQr
Supplementary Information [Line Items]
Business Acquisition, Effective Date of Acquisition	Apr. 15, 2016
Purchase Consideration		$ 225