Earnings Per Share - Treasury stock method (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share
Net income attributable to common shareholders	$ 11,474	$ 8,348	$ 16,837	$ 14,784
Weighted-average common shares outstanding for basic earnings per share	17,111	13,810	17,091	13,796
Basic earnings per common share	$ 0.66	$ 0.60	$ 0.97	$ 1.07
Dilutive effect of stock-based awards	334	290	334	293
Weighted-average common shares outstanding for diluted earnings per share	17,445	14,100	17,425	14,089
Diluted earnings per common share	$ 0.65	$ 0.59	$ 0.95	$ 1.05