Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Before Tax Amount
Other comprehensive income, net	$ 3,278	$ 7,427	$ 12,254	$ 13,265
Tax Benefit (Expense)
Other comprehensive income, net	(802)	(1,930)	(3,085)	(3,619)
Net of Tax Amount
Other comprehensive income, net	2,476	5,497	9,169	9,646
Unrealized Gains (Losses) on Available for  Sale Securities
Before Tax Amount
Net unrealized holding gains arising during period	3,329	7,852	13,124	13,961
Reclassification adjustment for net gains arising during the period			(342)	0
Other comprehensive income, net			12,782	13,961
Tax Benefit (Expense)
Net unrealized holding gains arising during period	(817)	(2,076)	(3,328)	(3,822)
Reclassification adjustment for net gains arising during the period			88	0
Other comprehensive income, net			(3,240)	(3,822)
Net of Tax Amount
Net unrealized holding gains arising during period	2,512	5,776	9,796	10,139
Reclassification adjustment for net gains arising during the period			(254)	0
Other comprehensive income, net			9,542	10,139
Unrealized Gains (Losses) on Derivatives
Before Tax Amount
Other comprehensive income, net	(51)	(425)	(528)	(696)
Tax Benefit (Expense)
Other comprehensive income, net	15	146	155	203
Net of Tax Amount
Other comprehensive income, net	$ (36)	$ (279)	$ (373)	$ (493)