Acquisitions and Divestitures (Summary of Allocation of Total Purchase Consideration) (Details) $ in Millions	6 Months Ended
	Jan. 27, 2018 USD ($) acquisition
Business Acquisition [Line Items]
Purchase Consideration	$ 788
Net Tangible Assets Acquired (Liabilities Assumed)	(31)
Purchased Intangible Assets	361
Goodwill	$ 458
Number of business combinations (acquisition) | acquisition	5
Viptela
Business Acquisition [Line Items]
Purchase Consideration	$ 497
Net Tangible Assets Acquired (Liabilities Assumed)	(18)
Purchased Intangible Assets	180
Goodwill	335
Springpath
Business Acquisition [Line Items]
Purchase Consideration	248
Net Tangible Assets Acquired (Liabilities Assumed)	(11)
Purchased Intangible Assets	160
Goodwill	99
Others (three in total)
Business Acquisition [Line Items]
Purchase Consideration	43
Net Tangible Assets Acquired (Liabilities Assumed)	(2)
Purchased Intangible Assets	21
Goodwill	$ 24
Number of business combinations (acquisition) | acquisition	3