Derivative Instruments (Gains and Losses on Derivatives Designated as Cash Flow Hedges) (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Apr. 30, 2011	May 01, 2010	Apr. 30, 2011	May 01, 2010
Gains (losses) recognized in OCI on derivatives (effective portion)	$ 51	$ (21)	$ 96	$ 11
Gains (losses) reclassified from AOCI into income (effective portion)	34	(2)	61	6
Operating Expenses [Member] | Foreign Currency Derivatives [Member]
Gains (losses) reclassified from AOCI into income (effective portion)	28	(2)	51	5
Cost of Sales-Service [Member] | Foreign Currency Derivatives [Member]
Gains (losses) reclassified from AOCI into income (effective portion)	5		9	1
Interest Expense [Member] | Interest Rate Derivatives [Member]
Gains (losses) reclassified from AOCI into income (effective portion)	1		1
Foreign Currency Derivatives [Member]
Gains (losses) recognized in OCI on derivatives (effective portion)	51	(21)	96	(12)
Interest Rate Derivatives [Member]
Gains (losses) recognized in OCI on derivatives (effective portion)				$ 23