Other Comprehensive Income - Summary of Change in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 262,830	$ 243,910	$ 211,784
Comprehensive Income (Loss)	10,935	(3,653)	15
Reclassification of Disproportionate Tax Effect			0
Ending balance	304,966	262,830	243,910
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3,996)	(343)	(121)
Comprehensive Income (Loss)	10,935	(3,653)	15
Reclassification of Disproportionate Tax Effect	0	0	(237)
Ending balance	6,939	(3,996)	(343)
Unrealized gains (losses) on securities available for sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3,534)	473	1,393
Comprehensive Income (Loss)	10,732	(4,007)	(1,004)
Reclassification of Disproportionate Tax Effect	0	0	84
Ending balance	7,198	(3,534)	473
Unrealized gain (loss) on postretirement benefits plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(304)	(690)	(1,217)
Comprehensive Income (Loss)	428	386	825
Reclassification of Disproportionate Tax Effect	0	0	(298)
Ending balance	124	(304)	(690)
Unrealized loss on interest rate swap
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(158)	(126)	(297)
Comprehensive Income (Loss)	(225)	(32)	194
Reclassification of Disproportionate Tax Effect	0	0	(23)
Ending balance	$ (383)	$ (158)	$ (126)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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Amount of increase (decrease) in accumulated other comprehensive income (AOCI) for reclassification to retained earnings of tax effect from remeasurement of deferred tax pursuant to Tax Cuts and Jobs Act.

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