Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Before Tax Amount
Other comprehensive income (loss), net	$ 1,656	$ (598)	$ (7,117)	$ 11,656
Tax Benefit (Expense)
Other comprehensive income (loss), net	(487)	59	2,234	(3,026)
Net of Tax Amount
Net current period other comprehensive income				8,884
Reclassification adjustment for net gains arising during the period				(254)
Other comprehensive income, net of tax	1,169	(539)	(4,883)	8,630
Net unrealized holding (losses) gains arising during period
Before Tax Amount
Net unrealized holding losses arising during period	(2,008)	(649)	(10,916)	12,475
Reclassification adjustment for net gains arising during the period			0	(342)
Other comprehensive income (loss), net			(10,916)	12,133
Tax Benefit (Expense)
Net unrealized holding losses arising during period	504	73	3,390	(3,255)
Reclassification adjustment for net gains arising during the period			0	88
Other comprehensive income (loss), net			3,390	(3,167)
Net of Tax Amount
Net current period other comprehensive income	(1,504)	(576)	(7,526)	9,220
Reclassification adjustment for net gains arising during the period			0	(254)
Other comprehensive income, net of tax			(7,526)	8,966
Net gain on securities reclassified from available for sale to held to maturity
Before Tax Amount
Other comprehensive income (loss), net	3,814	0	3,814	0
Tax Benefit (Expense)
Other comprehensive income (loss), net	(1,030)	0	(1,030)	0
Net of Tax Amount
Other comprehensive income, net of tax	2,784	0	2,784	0
Amortization of Gain on Debt Securities Reclassified to Held to Maturity
Before Tax Amount
Other comprehensive income (loss), net	(158)	0	(158)	0
Tax Benefit (Expense)
Other comprehensive income (loss), net	42	0	42	0
Net of Tax Amount
Other comprehensive income, net of tax	(116)	0	(116)	0
Unrealized gains on derivatives
Before Tax Amount
Other comprehensive income (loss), net	8	51	143	(477)
Tax Benefit (Expense)
Other comprehensive income (loss), net	(3)	(14)	(168)	141
Net of Tax Amount
Net current period other comprehensive income				(336)
Reclassification adjustment for net gains arising during the period				0
Other comprehensive income, net of tax	$ 5	$ 37	$ (25)	$ (336)