Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Basic and Diluted Earnings per share
Weighted average basic common shares outstanding	23,132	23,424	23,294	23,354
Dilutive effect of contingently convertible notes and warrants	0	1,003	0	2,004
Dilutive effect of employee stock purchases, net of assumed repurchase of treasury stock	5	5	4	5
Weighted average dilutive common shares outstanding	23,137	24,432	23,298	25,363
Basic:
Net income	$ 45,261	$ 26,162	$ 127,385	$ 74,327
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic	$ 1,729	$ 1,035	$ 4,906	$ 2,958
Basic earnings per common share	$ 1.88	$ 1.07	$ 5.26	$ 3.06
Earnings available to basic common shares	$ 43,532	$ 25,127	$ 122,479	$ 71,369
Diluted:
Net income	45,261	26,162	127,385	74,327
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted	1,729	1,000	4,905	2,769
Earnings available to diluted common shares	$ 43,532	$ 25,162	$ 122,480	$ 71,558
Diluted earnings per common share	$ 1.88	$ 1.03	$ 5.26	$ 2.82