Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Numerator:
Net Earnings (Loss)	$ 13,671	$ 5,855	$ 18,995	$ 11,721
Denominator:
Basic - Average Shares Outstanding (in shares)	18,594,207	18,941,131	18,658,182	18,952,093
Employee stock options (in shares)	609,356	526,422	604,287	538,963
Diluted - Weighted Average Shares Outstanding (in shares)	19,203,563	19,467,553	19,262,469	19,491,056
Basic Earnings per Share (in dollars per share)	$ 0.74	$ 0.31	$ 1.02	$ 0.62
Diluted Earnings per Share (in dollars per share)	$ 0.71	$ 0.30	$ 0.99	$ 0.60
Anti-dilutive securities excluded from earnings per share calculation (in shares)	253,781	179,130	208,578	127,289