Derivative Instruments and Other Hedging Activities - Reconciliation of Gross Amounts in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivative assets
Gross derivative assets	$ 265,589	$ 100,781
Gross amounts not offset in the Balance Sheet, derivatives	(9,490)	(5,111)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	256,099	95,670
Derivative liabilities
Gross derivative liabilities	12,141	10,606
Gross amounts not offset in the Balance Sheet, derivatives	(9,490)	(5,111)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative liabilities	2,651	5,495
Written and purchased options
Derivative assets
Gross derivative assets	1,602	3,871
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	1,602	3,871
Derivative liabilities
Gross derivative liabilities	1,602	3,871
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	1,602	3,871
Designated as Hedging Instruments | Interest rate contracts
Derivative assets
Gross derivative assets	41,200	18,967
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	41,200	18,967
Derivative liabilities
Gross derivative liabilities	11
Gross amounts not offset in the Balance Sheet, derivatives	0
Gross amounts not offset in the Balance Sheet, collateral	0
Net derivative liabilities	11
Not Designated as Hedging Instruments | Interest rate contracts
Derivative assets
Gross derivative assets	222,787	77,943
Gross amounts not offset in the Balance Sheet, derivatives	(9,490)	(5,111)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative assets	213,297	72,832
Derivative liabilities
Gross derivative liabilities	10,528	6,735
Gross amounts not offset in the Balance Sheet, derivatives	(9,490)	(5,111)
Gross amounts not offset in the Balance Sheet, collateral	0	0
Net derivative liabilities	$ 1,038	$ 1,624