Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator:
Net Earnings	$ 10,617	$ 8,745	$ 29,930	$ 27,740
Denominator:
Basic - Average Shares Outstanding (in shares)	18,267,828	18,468,546	18,288,083	18,594,508
Effect of dilutive securities - share-based compensation plans	543,810	572,329	535,662	560,336
Diluted - Weighted Average Shares Outstanding (in shares)	18,811,638	19,040,875	18,823,745	19,154,844
Basic Earnings per Share (in dollars per share)	$ 0.58	$ 0.47	$ 1.64	$ 1.49
Diluted Earnings per Share (in dollars per share)	$ 0.56	$ 0.46	$ 1.59	$ 1.45
Anti-dilutive securities excluded from earnings per share calculation (in shares)	147,737	251,704	251,576	268,698