Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net Earnings	$ 15,328	$ 14,817	$ 19,767	$ 19,843
Denominator:
Basic - Weighted Average Shares Outstanding	17,508,022	18,197,431	17,526,107	18,240,027
Effect of dilutive securities:
Share-based compensation plans	425,221	474,609	428,060	484,832
Diluted - Weighted Average Shares Outstanding	17,933,243	18,672,040	17,954,167	18,724,859
Basic Earnings per Share	$ 0.88	$ 0.81	$ 1.13	$ 1.09
Diluted Earnings per Share	$ 0.85	$ 0.79	$ 1.10	$ 1.06
Anti-dilutive securities excluded from earnings per share calculation	408,979	237,405	405,123	215,767