Income Taxes - Components of Net Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Allowance for loan losses	$ 3,047	$ 4,480
Nonaccrual loan interest	444	610
Other real estate owned valuation allowance	150	199
Deferred compensation	835	1,335
Net unrealized losses on securities	226	81
Acquisition accounting adjustments	1,283	3,215
Accrued pension liability	170	100
Other	488	796
Total deferred tax assets	6,643	10,816
Deferred tax liabilities:
Depreciation	761	1,030
Accretion of discounts on securities	24	113
Core deposit intangibles	267	602
Trust preferred fair value adjustment	349	581
Other	201	243
Total deferred tax liabilities	1,602	2,569
Net deferred tax assets	$ 5,041	$ 8,247