Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Before Tax Amount
Other comprehensive income (loss)	$ (598)	$ 1,800	$ 11,656	$ 15,065
Tax Benefit (Expense)
Other comprehensive income (loss)	59	(398)	(3,026)	(4,017)
Net of Tax Amount
Other comprehensive income (loss) before classifications			8,884	11,048
Reclassification adjustment for net gains arising during the period			(254)	0
Other comprehensive income, net of tax	(539)	1,402	8,630	11,048
Unrealized Gains (Losses) on Available for  Sale Securities
Before Tax Amount
Other comprehensive income (loss), before reclassifications			12,475	15,872
Reclassification adjustment for net gains arising during the period			(342)	0
Other comprehensive income (loss)	(649)	1,911	12,133	15,872
Tax Benefit (Expense)
Other comprehensive income (loss) before reclassifications			(3,255)	(4,253)
Reclassification adjustment for net gains arising during the period			88	0
Other comprehensive income (loss)	73	(431)	(3,167)	(4,253)
Net of Tax Amount
Other comprehensive income (loss) before classifications			9,220	11,619
Reclassification adjustment for net gains arising during the period			(254)	0
Other comprehensive income, net of tax	(576)	1,480	8,966	11,619
Unrealized Gains (Losses) on Derivatives
Before Tax Amount
Other comprehensive income (loss)	51	(111)	(477)	(807)
Tax Benefit (Expense)
Other comprehensive income (loss)	(14)	33	141	236
Net of Tax Amount
Other comprehensive income (loss) before classifications			(336)	(571)
Reclassification adjustment for net gains arising during the period			0	0
Other comprehensive income, net of tax	$ 37	$ (78)	$ (336)	$ (571)