Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Before Tax Amount
Other comprehensive income, net	$ 8,976	$ 5,838
Tax Benefit (Expense)
Other comprehensive income, net	(2,283)	(1,689)
Net of Tax Amount
Other comprehensive income, net	6,693	4,149
Unrealized Gains (Losses) on Available for Sale Securities
Before Tax Amount
Net unrealized holding gains arising during period	9,796	6,109
Reclassification adjustment for net gains arising during the period	(342)	0
Other comprehensive income, net	9,454	6,109
Tax Benefit (Expense)
Net unrealized holding gains arising during period	(2,512)	(1,746)
Reclassification adjustment for net gains arising during the period	88	0
Other comprehensive income, net	(2,424)	(1,746)
Net of Tax Amount
Net unrealized holding gains arising during period	7,284	4,363
Reclassification adjustment for net gains arising during the period	(254)	0
Other comprehensive income, net	7,030	4,363
Unrealized Gains (Losses) on Derivatives
Before Tax Amount
Other comprehensive income, net	(478)	(271)
Tax Benefit (Expense)
Other comprehensive income, net	141	57
Net of Tax Amount
Other comprehensive income, net	$ (337)	$ (214)