Fair Value (Fair Value, Nonrecurring Measurement) (Details) - Fair Value, Measurements, Nonrecurring - Level 3 - USD ($) $ in Millions	3 Months Ended
	Oct. 28, 2017	Oct. 29, 2016
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	$ (21)	$ (89)
Investments in privately held companies (impaired)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	(21)	(47)
Purchased intangible assets (impaired)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	$ 0	$ (42)