Fair Value (Fair Value, Nonrecurring Measurement) (Details) - Fair Value, Measurements, Nonrecurring - Level 3 - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 27, 2018	Jan. 28, 2017	Jan. 27, 2018	Jan. 28, 2017
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	$ 2	$ (88)	$ (19)	$ (177)
Investments in privately held companies (impaired)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	(18)	(64)	(39)	(111)
Purchased intangible assets (impaired)
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	0	0	0	(42)
Property held for sale—land and buildings
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	$ 20	$ (24)	$ 20	$ (24)