Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator:
Net Earnings	$ 15,523	$ 14,254	$ 21,318	$ 19,313
Denominator:
Basic - Weighted Average Shares Outstanding	18,167,054	18,253,326	18,242,240	18,298,379
Effect of dilutive securities:
Share-based compensation plans	508,553	534,554	534,129	537,163
Diluted - Weighted Average Shares Outstanding	18,675,607	18,787,880	18,776,369	18,835,542
Basic Earnings per Share	$ 0.85	$ 0.78	$ 1.17	$ 1.06
Diluted Earnings per Share	$ 0.83	$ 0.76	$ 1.14	$ 1.03
Anti-dilutive securities excluded from earnings per share calculation	154,897	278,862	155,497	270,433