Income Taxes - Components of Net Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Allowance for loan losses	$ 908	$ 985
Interest on non-accrual loans	130	89
Other real estate	446	419
Pension plan	242	233
Postretirement benefits	184	227
Unrealized losses (gains) on available-for-sale securities	268	(55)
Deferred compensation	191	162
Stock-based compensation	30	31
Other	27	20
Total deferred tax assets	2,426	2,111
Deferred tax liabilities
Depreciation	(126)	(171)
Amortization of goodwill	(955)	(955)
Net deferred loan fees and costs	(133)	(110)
Other	(58)	(64)
Total deferred tax (liabilities)	(1,272)	(1,300)
Net deferred tax assets	$ 1,154	$ 811