Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Income	$ 29,326	$ 26,534	$ 24,662
Basic Shares, in Shares	13,893	13,792	13,680
Basic Earnings, in USD Per Share	$ 2.11	$ 1.92	$ 1.80
Dilutive Average Shares Attributable to Stock Options, in Shares	93	88	50
Weighted Average Shares - Diluted, in Shares	13,986	13,880	13,730
Diluted Earnings, In USD Per Share	$ 2.10	$ 1.91	$ 1.80