Fair Value - Fair Value On Nonrecurring Basis (Details) - Nonrecurring - Level 3 - USD ($) $ in Millions	12 Months Ended
	Jul. 27, 2019	Jul. 28, 2018	Jul. 29, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	$ (32)	$ (43)	$ (254)
Non-marketable equity securities and equity method investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	(32)	(62)	(177)
Purchased intangible assets (impaired)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	0	(1)	(47)
Property held for sale - land and buildings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total gains (losses) for nonrecurring measurements	$ 0	$ 20	$ (30)