Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Before Tax Amount
Other comprehensive (losses) income, net	$ (18,570)	$ 8,976
Tax Benefit (Expense)
Other comprehensive (losses) income, net	5,482	(2,283)
Net of Tax Amount
Other comprehensive (loss) income before classifications	(13,088)	6,947
Reclassification adjustment for net gains arising during the period	0	(254)
Other comprehensive income, net of tax	(13,088)	6,693
Net unrealized gains (losses) on available for sale securities:
Before Tax Amount
Net unrealized holding gains arising during period	(18,637)	9,796
Reclassification adjustment for net gains arising during the period	0	(342)
Other comprehensive (losses) income, net	(18,637)	9,454
Tax Benefit (Expense)
Net unrealized holding gains arising during period	5,502	(2,512)
Reclassification adjustment for net gains arising during the period	0	88
Other comprehensive (losses) income, net	5,502	(2,424)
Net of Tax Amount
Other comprehensive (loss) income before classifications	(13,135)	7,284
Reclassification adjustment for net gains arising during the period	0	(254)
Other comprehensive income, net of tax	(13,135)	7,030
Unrealized gains (losses) on derivatives
Before Tax Amount
Other comprehensive (losses) income, net	67	(478)
Tax Benefit (Expense)
Other comprehensive (losses) income, net	(20)	141
Net of Tax Amount
Other comprehensive (loss) income before classifications	47	(337)
Reclassification adjustment for net gains arising during the period	0	0
Other comprehensive income, net of tax	$ 47	$ (337)