Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets, Gross [Abstract]
Allowance for credit losses	$ 10,116	$ 10,223
Postretirement benefits other than pensions	311	345
Alternative minimum tax credit carryforward	216	201
Unrealized loss on securities available for sale	3,137	2,091
Deferred Tax Assets, Operating Loss Carryforwards	3,636	6,145
Writedown of other real estate owned	711	878
Deferred compensation	1,426	1,514
Accrued interest on nonaccrual loans	629	1,017
Accrued incentives	2,477	1,277
Unfunded loan commitments & other reserves	1,064	1,098
Deferred rent	799	801
Other	1,486	1,224
Total deferred tax assets	26,008	26,814
Deferred tax liabilities:
Income from unconsolidated subsidiary	(11)	(380)
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(1,378)	(587)
Other	(1,053)	(338)
Total deferred tax liabilities	(2,442)	(1,305)
Net deferred tax asset	$ 23,566	$ 25,509