Changes in the Servicing Assets (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Servicing Assets at Fair Value [Line Items]
Carrying amount before valuation allowance as of the beginning of the period			$ 1,392	$ 1,440
Servicing rights that result from the transfer of residential mortgage or automobile loans			48	60
Amortization	$ (37)	$ (34)	(111)	(89)
Carrying amount before valuation allowance	1,329	1,411	1,329	1,411
Valuation allowance for servicing assets:
Beginning balance			(534)	(469)
(Provision for) recovery of MSR impairment			(38)	(7)
Ending balance	(572)	(476)	(572)	(476)
Carrying amount as of the end of the period	$ 757	$ 935	$ 757	$ 935	$ 858