Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator:
Net Earnings (Loss)	$ 8,745	$ 9,728	$ 27,740	$ 21,449
Denominator:
Basic - Average Shares Outstanding (in shares)	18,468,546	18,741,524	18,594,508	18,881,132
Employee stock options (in shares)	572,329	529,550	560,336	535,929
Diluted - Weighted Average Shares Outstanding (in shares)	19,040,875	19,271,074	19,154,844	19,417,061
Basic Earnings per Share (in dollars per share)	$ 0.47	$ 0.52	$ 1.49	$ 1.14
Diluted Earnings per Share (in dollars per share)	$ 0.46	$ 0.50	$ 1.45	$ 1.10
Anti-dilutive securities excluded from earnings per share calculation (in shares)	251,704	180,551	268,698	145,238