Derivative Instruments (Offsetting of Derivative Assets and Liabilities) (Details) - USD ($) $ in Millions	Apr. 29, 2017	Jul. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Amount of Recognized, Assets	$ 123	$ 385
Gross Amounts Offset, Assets	0	0
Net Amounts Presented, Assets	123	385
Gross Derivative Amounts, Assets	(16)	(23)
Cash Collateral, Assets	(78)	(305)
Net Amount, Assets	29	57
Gross Amount of Recognized, Liabilities	23	54
Gross Amounts Offset, Liabilities	0	0
Net Amount Presented, Liabilities	23	54
Gross Derivative Amounts, Liabilities	(16)	(23)
Cash Collateral, Liabilities	0	0
Net Amount, Liabilities	$ 7	$ 31