Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share
Shares not included in computation of diluted weighted average earnings per common	275	700
Net income attributable to common shareholders	$ 6,261	$ 7,839
Basic weighted average common shares outstanding	6,104	6,114
Potentially dilutive common shares	152	149
Diluted weighted average common shares outstanding	6,256	6,263
Basic earnings per common share: (in dollars per share)	$ 1.03	$ 1.28
Diluted earnings common share (in dollars per share)	$ 1.00	$ 1.25