Net Earnings Per Common Share Computation of Basic and Diluted Net Earnings Per Common Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Basic
Average common shares outstanding									31,958	32,393	31,969
Net earnings (loss)	$ (35,028)	$ 12,800	$ 10,661	$ 7,454	$ 7,248	$ 15,598	$ (611)	$ 3,106	$ (4,113)	$ 25,341	$ 41,179
Net earnings per common share	$ (1.10)	$ 0.40	$ 0.33	$ 0.23	$ 0.22	$ 0.48	$ (0.02)	$ 0.10	$ (0.13)	$ 0.78	$ 1.29
Diluted
Average common shares outstanding									31,958	32,393	31,969
Shares related to convertible debt									0	163	0
Stock options and awards									0	138	27
Average common shares assuming dilution									31,958	32,694	31,996
Net Earnings (loss)	$ (35,028)	$ 12,800	$ 10,661	$ 7,454	$ 7,248	$ 15,598	$ (611)	$ 3,106	$ (4,113)	$ 25,341	$ 41,179
Net Earnings (loss) per Share - Assuming Dilution	$ (1.10)	$ 0.40	$ 0.32	$ 0.23	$ 0.22	$ 0.48	$ (0.02)	$ 0.09	$ (0.13)	$ 0.78	$ 1.29