Derivative Instruments (Effect Of Derivative Instruments Designated As Cash Flow Hedges And Underlying Hedged Items On Consolidated Statements Of Operations Summary) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 28, 2012	Jan. 29, 2011	Jan. 28, 2012	Jan. 29, 2011
Derivative [Line Items]
Gains (losses) recognized in OCI on derivatives (effective portion)	$ (44)	$ (10)	$ (94)	$ 45
Gains (losses) reclassified from AOCI into income (effective portion)	(26)	20	(26)	27
Foreign Currency Derivatives [Member]
Derivative [Line Items]
Gains (losses) recognized in OCI on derivatives (effective portion)	(44)	(10)	(94)	45
Operating Expenses [Member] | Foreign Currency Derivatives [Member]
Derivative [Line Items]
Gains (losses) reclassified from AOCI into income (effective portion)	(22)	17	(22)	23
Cost Of Sales-Service [Member]
Derivative [Line Items]
Gains (losses) reclassified from AOCI into income (effective portion)	$ (4)	$ 3	$ (4)	$ 4