Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Deferred Tax Asset, Tax Deferred Expense, Lease Liability	$ 11,203	$ 0
Deferred Tax Assets, Gross [Abstract]
Allowance for credit losses	10,937	10,116
Postretirement benefits other than pensions	275	311
Alternative minimum tax credit carryforward	216	216
Unrealized loss on securities available for sale	0	3,137
Deferred Tax Assets, Operating Loss Carryforwards	2,017	3,636
Writedown of other real estate owned	48	711
Deferred compensation	1,720	1,426
Accrued interest on nonaccrual loans	710	629
Accrued incentives	2,185	2,477
Unfunded loan commitments & other reserves	964	1,064
Deferred rent	28	799
Other	956	1,486
Total deferred tax assets	31,259	26,008
Deferred tax liabilities:
Deferred Tax Liabilities, Leasing Arrangements	10,302	0
Net Unrealized Gain On Investment Securities Available For Sale	1,386	0
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(1,470)	(1,378)
Other	(1,239)	(1,064)
Total deferred tax liabilities	(14,397)	(2,442)
Net deferred tax asset	$ 16,862	$ 23,566