Comprehensive Income - Summary of Changes in Components of Other Comprehensive Income, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ 768,065	$ 736,922	$ 763,784	$ 725,263
Other comprehensive (loss) income before classifications			(6,052)	9,423
Amounts reclassified from accumulated other comprehensive income			0	(254)
Other comprehensive income, net of tax	7,036	2,476	(6,052)	9,169
Balance at end of period	796,676	745,489	796,676	745,489
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(1,691)	8,941	11,397	2,248
Other comprehensive income, net of tax	7,036	2,476	(6,052)	9,169
Balance at end of period	5,345	11,417	5,345	11,417
Net unrealized gains (losses) on available for sale securities:
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(1,733)	8,966	11,402	1,936
Other comprehensive (loss) income before classifications	7,113	2,512	(6,022)	9,796
Amounts reclassified from accumulated other comprehensive income	0	0	0	(254)
Other comprehensive income, net of tax	7,113	2,512	(6,022)	9,542
Balance at end of period	5,380	11,478	5,380	11,478
Unrealized gains (losses) on derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	72	(20)	25	317
Other comprehensive (loss) income before classifications			(30)	(373)
Amounts reclassified from accumulated other comprehensive income			0	0
Other comprehensive income, net of tax	(77)	(36)	(30)	(373)
Balance at end of period	(5)	(56)	(5)	(56)
Pension Items
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(30)	(5)	(30)	(5)
Other comprehensive (loss) income before classifications			0	0
Amounts reclassified from accumulated other comprehensive income			0	0
Other comprehensive income, net of tax	0	0	0	0
Balance at end of period	$ (30)	$ (5)	$ (30)	$ (5)