Acquisitions and Divestitures (Summary Of Allocation Of Total Purchase Consideration) (Details) $ in Millions	3 Months Ended
	Oct. 24, 2015 USD ($)
Business Acquisition [Line Items]
Purchase Consideration	$ 656
Net Liabilities Assumed	(31)
Purchased Intangible Assets	130
Goodwill	557
MaintenanceNet
Business Acquisition [Line Items]
Purchase Consideration	105
Net Liabilities Assumed	(21)
Purchased Intangible Assets	65
Goodwill	61
OpenDNS
Business Acquisition [Line Items]
Purchase Consideration	545
Net Liabilities Assumed	(9)
Purchased Intangible Assets	61
Goodwill	493
Other
Business Acquisition [Line Items]
Purchase Consideration	6
Net Liabilities Assumed	(1)
Purchased Intangible Assets	4
Goodwill	$ 3