Activity Related to the MSR Portfolio (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Servicing Assets at Fair Value [Line Items]
Gain Loss On Sale Of Securities Net Economic Hedge Servicing Rights	$ 5	$ 6	$ 5	$ 12
Changes Fair Value Of Free Standing Derivatives	32	235	75	338
Mortgage Servicing Rights (MSR) Impairment (Recovery)	$ (72)	$ (201)	$ (122)	$ (228)