Earnings Per Share - Schedule of Dilutive Effect of Stock Options RSUs and PSAs (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net Income	$ 13,617	$ 11,937	$ 26,034	$ 22,114
Basic	18,806	18,775	18,738	18,840
Dilutive effect of stock options, RSUs, and performance shares	403	311	470	412
Weighted-average number of diluted shares outstanding during the period	19,209	19,086	19,208	19,252
Basic	$ 0.72	$ 0.64	$ 1.39	$ 1.17
Diluted	$ 0.71	$ 0.63	$ 1.36	$ 1.15