Changes in the Servicing Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Servicing Assets at Fair Value
Carrying amount as of the beginning of the period	$ 1,358	$ 1,239
Servicing Obligations From Transfers		121
Servicing Asset At Amortized Value Amortization	(53)	(46)
Carrying amount before valuation allowance	1,384	1,314
Valuation allowance for servicing assets:
Beginning balance	(661)	(558)
Servicing impairment	49	11
Ending balance	(612)	(547)
Carrying amount as of the end of the period	772	767
Residential Mortgage
Servicing Assets at Fair Value
Servicing Obligations From Transfers	73
Automobile Loan Securitizations
Servicing Assets at Fair Value
Servicing Obligations From Transfers	$ 6