Income Taxes - Components of net deferred income tax benefits (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax benefits:
Accrued deferred compensation	$ 78	$ 92
Allowance for credit losses	347	7
Nonaccrual interest		375
Alternative minimum tax credits		1,191
Net operating loss carryforward credits	345	297
Accumulated depreciation		(15)
Accumulated depreciation	4
Other real estate owned		3
Reserve for unfunded commitments	10	7
Accounting standard 310-20	(76)
Other temporary differences	7	20
Accumulated securities premium accretion	210	213
Net unrealized depreciation on investment securities available for sale	467	239
Net deferred income tax benefits	$ 1,392	$ 2,429