Derivative Instruments Derivative Instruments (Derivatives Offset in Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Jan. 25, 2014	Jul. 27, 2013
Derivative Asset, Fair Value, Amount Not Offset Against Collateral [Abstract]
Derivative Asset, Gross Amount	$ 164	$ 182
Gross Derivative Amounts offset in Balance Sheet	0	0
Derivative Asset, Net Amount in Balance Sheet	164	182
Gross Derivative Amounts Eligible for Offsetting	(48)	(120)
Net Amount	116	62
Derivative Liability, Gross Amount	53	171
Gross Derivative Amounts Offset in Balance Sheet	0	0
Derivative Liability, Net Amount in Balance Sheet	53	171
Gross Derivative Amounts Eligible for Offsetting	(48)	(120)
Net Amount	$ 5	$ 51