Loans and Loans Held for Sale - Summary of Changes in Loans Held for Sale (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Loans Receivable Held For Sale Net [Abstract]
Balance at beginning of the period	$ 599	$ 628	$ 728
New originations	1,075	1,686	935
Transfers from held to maturity, net	19	38	19
Loan sales	(1,257)	(1,747)	(1,168)
Loan draws (payments), net		(4)	(3)
Transfers to OREO / valuation adjustments	(2)	(2)
Balance at end of period	$ 434	$ 599	$ 511

The aggregate carrying amount of loans receivable that will be sold to other entities. Includes mortgage and all other loans (collectively, loans) not classified as held for investment. Such loans are stated at the lower of cost or market, or elected fair value. Mortgage loans exclude mortgage-backed securities which are considered a debt security (other loan).

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