Income Taxes - Tax Effects of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Allowance for loan losses	$ 1,287	$ 1,885
Funded status of pension plan	1,286	1,964
Deferred compensation	272	414
Securities impairment	199	149
Net unrealized loss on securities	180	349
Accrued incentive compensation	136	158
Stock compensation	77	160
Nonaccrual loan interest income	53	73
Business combination adjustments	38	89
Net operating loss carryforward	0	106
Other	35	29
Gross deferred tax assets	3,563	5,376
Deferred tax liabilities:
Accrued pension liability	939	1,525
Depreciation	652	1,006
Deferred loan fees and costs	307	431
Intangible assets	204	324
Other	52	60
Gross deferred tax liabilities	2,154	3,346
Net deferred tax asset	$ 1,409	$ 2,030