Derivative Instruments and Other Hedging Activities - Reconciliation of Gross Amounts in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivative assets
Gross derivative assets	$ 100,781	$ 24,174
Gross amounts not offset in the Balance Sheet, derivatives	(5,111)	(619)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	95,670	23,555
Derivative liabilities
Gross derivative liabilities	10,606	21,288
Gross amounts not offset in the Balance Sheet, derivatives	(5,111)	(619)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative liabilities	5,495	20,669
Written and purchased options
Derivative assets
Gross derivative assets	3,871	3,285
Gross amounts not offset in the Balance Sheet, derivatives	0	0
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	3,871	3,285
Derivative liabilities
Gross derivative liabilities	3,871	3,285
Gross amounts not offset in the Balance Sheet, derivatives	0	0
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative liabilities	3,871	3,285
Derivatives designated as hedging instruments | Interest rate contracts
Derivative assets
Gross derivative assets	18,967	3,469
Gross amounts not offset in the Balance Sheet, derivatives	0	0
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	18,967	3,469
Derivatives not designated as hedging instruments | Interest rate contracts
Derivative assets
Gross derivative assets	77,943	17,420
Gross amounts not offset in the Balance Sheet, derivatives	(5,111)	(619)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	72,832	16,801
Derivative liabilities
Gross derivative liabilities	6,735	18,003
Gross amounts not offset in the Balance Sheet, derivatives	(5,111)	(619)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative liabilities	$ 1,624	$ 17,384