Derivative Instruments (Effect Of Derivative Instruments Designated As Cash Flow Hedges On Other Comprehensive Income And The Consolidated Statements Of Operations Summary) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Apr. 28, 2012	Apr. 30, 2011	Apr. 28, 2012	Apr. 30, 2011
Derivative [Line Items]
Gains (losses) recognized in OCI on derivatives (effective portion)	$ 11	$ 51	$ (83)	$ 96
Gains (losses) reclassified from AOCI into income (effective portion)	(18)	34	(44)	61
Foreign Currency Derivatives [Member]
Derivative [Line Items]
Gains (losses) recognized in OCI on derivatives (effective portion)	11	51	(83)	96
Operating Expenses [Member] | Foreign Currency Derivatives [Member]
Derivative [Line Items]
Gains (losses) reclassified from AOCI into income (effective portion)	(15)	28	(37)	51
Cost Of Sales-Service [Member]
Derivative [Line Items]
Gains (losses) reclassified from AOCI into income (effective portion)	(4)	5	(8)	9
Interest Expense [Member] | Interest Rate Derivatives [Member]
Derivative [Line Items]
Gains (losses) reclassified from AOCI into income (effective portion)	$ 1	$ 1	$ 1	$ 1