Loans - Outstanding Balance and Carrying Value of Acquired Loans (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Outstanding balance	$ 20,179		$ 21,151
Carrying value(1)	18,580		19,516
Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Outstanding balance	3,704		3,840
Carrying value(1)	2,537		2,629
Non-Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Outstanding balance	16,475		17,311
Carrying value(1)	16,043		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	35		$ 37
Provision for credit losses for Acquired Loans	$ (2)	$ 7