Fair Value (Reconciliation For All Assets Measured At Fair Value On Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Detail) (Level 3, USD $) In Millions, unless otherwise specified	12 Months Ended
	Jul. 28, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 123
Included in other income (loss), net	3
Included in other comprehensive income	(3)
Sales	(15)
Transfer into Level 2	107
Ending balance	1
Asset-Backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	121
Included in other income (loss), net	3
Included in other comprehensive income	(3)
Sales	(14)
Transfer into Level 2	107
Ending balance	0
Derivative Financial Instruments, Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	2
Sales	(1)
Ending balance	$ 1