Fair Value (Reconciliation For All Assets Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) (Level 3 [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
	Jan. 28, 2012	Jan. 29, 2011
Assets And Liabilities At Fair Value On A Recurring Basis [Line Items]
Beginning balance	$ 123	$ 152
Included in other income, net	3	(1)
Included in other comprehensive income	(3)
Sales and maturities	(15)	(11)
Transfers into Level 2	(107)
Ending balance	1	140
Losses attributable to assets still held		(1)
Derivative Assets [Member]
Assets And Liabilities At Fair Value On A Recurring Basis [Line Items]
Beginning balance	2	3
Included in other income, net		(1)
Sales and maturities	(1)
Ending balance	1	2
Losses attributable to assets still held		(1)
Asset-Backed Securities [Member]
Assets And Liabilities At Fair Value On A Recurring Basis [Line Items]
Beginning balance	121	149
Included in other income, net	3
Included in other comprehensive income	(3)
Sales and maturities	(14)	(11)
Transfers into Level 2	(107)
Ending balance		$ 138