Derivative Instruments (Offsetting of Derivative Assets and Liabilities) (Details) - USD ($) $ in Millions	Jan. 28, 2017	Jul. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Amount of Recognized, Assets	$ 118	$ 385
Gross Amounts Offset, Assets	0	0
Net Amounts Presented, Assets	118	385
Gross Derivative Amounts, Assets	(21)	(23)
Cash Collateral, Assets	(90)	(305)
Net Amount, Assets	7	57
Gross Amount of Recognized, Liabilities	59	54
Gross Amounts Offset, Liabilities	0	0
Net Amount Presented, Liabilities	59	54
Gross Derivative Amounts, Liabilities	(21)	(23)
Cash Collateral, Liabilities	0	0
Net Amount, Liabilities	$ 38	$ 31