Supplemental Comprehensive Income Disclosures - Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized holding (losses) gains on securities arising during the period	$ (29,892)	$ 19,981	$ 20,625
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	(6,278)	4,196	4,331
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	(23,614)	15,785	16,294
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	16	70	22
Less: reclassification adjustment for (gains) losses on securities included in net income, Tax (Expense) Benefit	3	15	5
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	13	55	17
OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, before Tax	29,908	(19,911)	(20,603)
Total Unrealized (Losses) Gains on Securities, Tax (Expense) Benefit	6,281	(4,181)	(4,326)
OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax	23,627	(15,730)	(16,277)
Unrealized holding (losses) gains on derivatives arising during the period	(3,356)	(4,467)	935
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	(705)	(938)	196
Unrealized holding gains on derivatives arising during the period, Net of Tax Amount	(2,651)	(3,529)	739
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	3,356	4,467	(935)
Total unrealized gains on derivatives, Tax (Expense) Benefit	705	938	(196)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	2,651	3,529	(739)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	76	537	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax	(16)	113	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax	(60)	424	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	(275)	155	121
Net (loss) gain, Tax (Expense) Benefit	(58)	32	25
Net gain	217	(123)	(96)
Total Unrealized Gains (Losses) for Postretirement Obligations, Before Tax	351	(692)	(121)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	74	(145)	(25)
Total Unrealized Gains (Losses) for Postretirement Obligations, Net of Tax	277	(547)	(96)
Total other comprehensive (loss) income, Pretax Amount	(32,913)	14,752	21,417
Other Comprehensive Income (Loss), Tax	(6,912)	3,098	4,497
Total other comprehensive (loss) Income	(26,001)	11,654	16,920
Post-Retirement Obligation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax	60
Net gain	217
Total other comprehensive (loss) Income	$ 277	$ (547)	$ (96)