Acquisitions and Divestitures (Additional Information) (Details) $ in Millions	2 Months Ended	12 Months Ended
	Oct. 24, 2015 USD ($)	Jul. 25, 2015 USD ($)	Jul. 26, 2014 USD ($)	Jul. 27, 2013 USD ($)
Business Acquisition [Line Items]
Number of business combinations (in numbers)		6
Acquired Cash and Cash Equivalents		$ 5	$ 134	$ 156
Purchase Consideration		334	3,181	6,982
General and Administrative Expense [Member]
Business Acquisition [Line Items]
Business Acquisition, Transaction Costs		$ 10	$ 7	$ 40
OpenDNS [Member] | Subsequent Event
Business Acquisition [Line Items]
Purchase Consideration	$ 635