Derivative Instruments (Offsetting of Derivative Assets and Liabilities) (Details) - USD ($) $ in Millions	Apr. 27, 2019	Jul. 28, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Amount of Recognized, Assets	$ 36	$ 2
Gross Amounts Offset, Assets	0	0
Net Amounts Presented, Assets	36	2
Gross Derivative Amounts, Assets	(10)	(2)
Cash Collateral, Assets	(26)	0
Net Amount, Assets	0	0
Gross Amount of Recognized, Liabilities	20	74
Gross Amounts Offset, Liabilities	0	0
Net Amount Presented, Liabilities	20	74
Gross Derivative Amounts, Liabilities	(10)	(2)
Cash Collateral, Liabilities	(5)	(53)
Net Amount, Liabilities	$ 5	$ 19