Loans - Outstanding Balance and Carrying Value of Acquired Loans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Outstanding balance	$ 16,506	$ 21,151
Carrying value	15,074	19,516
Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Outstanding balance	3,272	3,840
Carrying value	2,263	2,629
Non-Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Outstanding balance	13,234	17,311
Carrying value	12,811	16,887
Receivables Acquired with Deteriorated Credit Quality [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Financing Receivable, Allowance for Credit Losses	31	37
Provision for credit losses for Acquired Loans	$ (6)	$ 10