Income Taxes - Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Allowance for loan losses		$ 84
Real estate owned	$ 5
Accrued liabilities	173	218
State income taxes	33	46
Deferred compensation		494
Stock compensation	182	156
Net operating loss carryforward	4,367	5,886
Non-accrual loan interest	4	9
Partnership investment	101	175
General business credit	1,458	1,282
Alternative minimum tax credit	256	209
Other	14	37
Total deferred tax assets	6,593	8,596
Deferred tax liabilities:
Allowance for loan losses	(276)
Deferred loan fees/costs	(817)	(1,125)
Basis difference on fixed assets	(49)	(57)
Net unrealized appreciation on available-for-sale securities	(36)	(90)
FHLB stock dividends	(266)	(371)
Mortgage servicing rights	(7)	(13)
Prepaid expenses	(32)	(33)
Total deferred tax liabilities	(1,483)	(1,689)
Net deferred tax assets	$ 5,110	6,907
Valuation allowance
Period for which prior cumulative losses considered in assessing the realization of deferred tax assets	2 years
Valuation allowance	$ 0	$ 0