Asset Quality - Changes in Liability for Credit Losses on Lending Related Commitments (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Receivables [Abstract]
Balance at beginning of period	$ 69	$ 41	$ 56	$ 35
Provision (credit) for losses on lending-related commitments	(19)	4	(6)	10
Balance at end of period	$ 50	$ 45	$ 50	$ 45