Asset Quality - Changes in Liability for Credit Losses on Lending Related Commitments (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
Receivables [Abstract]
Balance at beginning of period	$ 37	$ 51	$ 29	$ 45
Provision (credit) for losses on lending-related commitments	3	(8)	11	(2)
Balance at end of period	$ 40	$ 43	$ 40	$ 43