Derivative Instruments (Offsetting of Derivative Assets and Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Oct. 25, 2014	Jul. 26, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross Amount of Recognized Assets	$ 227	$ 160
Gross Amounts Offset in Consolidated Balance Sheets	0	0
Net Amount Presented on Consolidated Balance Sheets	227	160
Gross Derivative Amounts with Legal Rights to Offset	(59)	(39)
Cash Collateral Received	(115)	(60)
Net Amount	53	61
Gross Amount of Recognized Liabilities	99	67
Gross Amounts Offset in Consolidated Balance Sheets	0	0
Net Amount Presented on Consolidated Balance Sheets	99	67
Gross Derivative Amounts with Legal Rights to Offset	(59)	(39)
Cash Collateral Pledged	0	(1)
Net Amount	$ 40	$ 27