Borrowed Funds - Schedule of Short-Term Borrowings (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total short-term borrowings	$ 1,076,991	$ 146,781
Short-term borrowings [Member]
Debt Instrument [Line Items]
Securities sold under agreements to repurchase	500,991	146,781
Federal funds purchased	50,000	0
FHLB advances	526,000	0
Total short-term borrowings	$ 1,076,991	$ 146,781