Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Deferred Tax Asset, Tax Deferred Expense, Lease Liability	$ 9,928	$ 11,203
Deferred Tax Assets, Gross [Abstract]
Allowance for credit losses	21,483	10,937
Postretirement benefits other than pensions	242	275
Alternative minimum tax credit carryforward	0	216
Deferred Tax Assets, Operating Loss Carryforwards	385	2,017
Deferred compensation	1,723	1,720
Accrued interest on nonaccrual loans	644	710
Accrued incentives	2,182	2,185
Unfunded loan commitments & other reserves	1,576	964
Other	1,831	1,032
Total deferred tax assets	39,994	31,259
Deferred tax liabilities:
Loan origination fees and costs	(1,280)	(626)
Deferred Tax Liabilities, Leasing Arrangements	9,037	10,302
Net Unrealized Gain On Investment Securities Available For Sale	4,629	1,386
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(2,103)	(1,470)
Section 197 intangibles	(540)	(45)
Other	(424)	(568)
Total deferred tax liabilities	(18,013)	(14,397)
Net deferred tax asset	$ 21,981	$ 16,862