Activity Related to the MSR Portfolio (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Servicing Assets at Fair Value
Securities gains, net - non-qualifying hedges on MSRs	$ 5	$ 5	$ 13	$ 5
Changes in fair value and settlement of free-standing derivatives purchased to economically hedge the MSR portfolio (Mortgage banking net revenue)	24	32	(13)	75
Recovery of (provision for) MSR impairment (Mortgage banking net revenue)	$ (1)	$ (72)	$ 150	$ (122)