Goodwill and Purchased Intangible Assets (Additional Information) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Purchased intangible assets impairment	$ 0	$ 0	$ 0	$ 42,000,000
Impairment charges	60,000,000	64,000,000	121,000,000	142,000,000
Restructuring and other charges
Acquired Finite-Lived Intangible Assets [Line Items]
Impairment charges	$ 0	$ 0	$ 0	$ 38,000,000