Derivative Instruments Derivative Instruments (Derivatives Offset in Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Apr. 26, 2014	Jul. 27, 2013
Derivative Asset, Fair Value, Amount Not Offset Against Collateral [Abstract]
Derivative Asset	$ 148	$ 182
Gross Amounts Offset in Consolidated Balance Sheets	0	0
Net Amount Presented on Consolidated Balance Sheets	148	182
Gross Derivative Amounts with Legal Rights to Offset	(36)	(120)
Cash Collateral Received	(5)	0
Net Amount	107	62
Derivative Liability, Gross Amount	54	171
Gross Amounts Offset in Consolidated Balance Sheets	0	0
Net Amount Presented on Consolidated Balance Sheets	54	171
Gross Derivative Amounts with Legal Rights to Offset	(36)	(120)
Derivative, Collateral, Right to Reclaim Cash	(16)	0
Net Amount	$ 2	$ 51