Fair Value (Reconciliation For All Assets Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Detail) (Fair Value, Inputs, Level 3 [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 29, 2011
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 123
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issuances, Settlements	(5)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	117
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Losses Attributable To Assets Still Held	(1)
Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	121
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issuances, Settlements	(5)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	116
Derivative Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	1
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Losses Attributable To Assets Still Held	$ (1)