Income per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Per Share
Net Income	$ 7,726	$ 8,898
Weighted average basic shares outstanding	1,826	1,853
Add: Effect of dilutive securities	6	6
Weighted average diluted shares outstanding	1,832	1,859
Earnings per share:
Basic	$ 4.23	$ 4.80
Diluted	$ 4.22	$ 4.79