Loans and Loans Held for Sale - Summary of Changes in Loans Held for Sale (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Loans Receivable Held For Sale Net [Abstract]
Balance at beginning of the period	$ 434	$ 628	$ 511
New originations	1,241	1,686	1,308
Transfers from held to maturity, net	17	38	7
Loan sales	(1,292)	(1,747)	(1,165)
Loan draws (payments), net		(4)	(4)
Transfers to OREO / valuation adjustments	2	(2)	(1)
Balance at end of period	$ 402	$ 599	$ 656

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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