Derivative Instruments (Offsetting of Derivative Assets and Liabilities) (Details) - USD ($) $ in Millions	Jan. 27, 2018	Jul. 29, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Amount of Recognized, Assets	$ 90	$ 149
Gross Amounts Offset, Assets	0	0
Net Amounts Presented, Assets	90	149
Gross Derivative Amounts, Assets	(32)	(4)
Cash Collateral, Assets	(18)	(81)
Net Amount, Assets	40	64
Gross Amount of Recognized, Liabilities	76	4
Gross Amounts Offset, Liabilities	0	0
Net Amount Presented, Liabilities	76	4
Gross Derivative Amounts, Liabilities	(32)	(4)
Cash Collateral, Liabilities	(18)	0
Net Amount, Liabilities	$ 26	$ 0