Earnings Per Share - Two-class method (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share
Net Income	$ 7,652	$ 7,104	$ 8,348	$ 6,436	$ 6,033	$ 7,370	$ 5,599	$ 6,864	$ 29,540	$ 25,866	$ 15,001
Dividends and undistributed earnings allocated to participating securities									647
Net income available to common shareholders									$ 28,893
Weighted-average common shares outstanding for basic earnings per share									14,736	13,763	13,653
Dilutive effect of stock-based awards									357	300	354
Weighted-average common shares outstanding for diluted earnings per share									15,093	14,063	14,007
Earnings per common share:
Basic earnings per common share	$ 0.44	$ 0.49	$ 0.60	$ 0.47	$ 0.44	$ 0.53	$ 0.41	$ 0.50	$ 1.96	$ 1.88	$ 1.10
Diluted earnings per common share	$ 0.43	$ 0.48	$ 0.59	$ 0.46	$ 0.43	$ 0.52	$ 0.40	$ 0.49	$ 1.91	$ 1.84	$ 1.07