Computation of earnings per share - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 4,356	$ 2,988	$ 9,137	$ 8,126
Less: Undistributed earnings allocated to participating securities	(67)	(48)	(131)	(110)
Net income allocated to common stock	4,288	2,940	9,006	8,016
Weighted-average common shares issued	2,843	2,823	2,835	2,815
Less: Unvested restricted stock awards	(44)	(40)	(41)	(34)
Weighted average common shares outstanding used to calculate basic earnings per common share	2,799	2,783	2,794	2,781
Add: Dilutive effect of stock options	8	12	8	12
Weighted-average common shares outstanding used to calculate diluted earnings per common share	$ 2,807	$ 2,795	$ 2,802	$ 2,793
Earnings per common share (basic)	$ 1.53	$ 1.06	$ 3.22	$ 2.88
Earnings per common share (diluted)	$ 1.53	$ 1.05	$ 3.21	$ 2.87