Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Basic and Diluted Earnings per share
Weighted average basic common shares outstanding	23,443	23,339
Dilutive effect of contingently convertible notes and warrants	0	2,085
Dilutive effect of employee stock purchases, net of assumed repurchase of treasury stock	3	4
Weighted average dilutive common shares outstanding	23,446	25,428
Basic:
Net income	$ 35,815	$ 31,303
Less: Earning allocated to participating securities	1,388	1,241
Earnings available to basic common shares	34,427	30,062
Basic earnings per common share	$ 1.47	$ 1.29
Diluted:
Net income	35,815	31,303
Less: Earning allocated to participating securities	1,388	1,156
Earnings available to diluted common shares	$ 34,427	$ 30,147
Diluted earnings per common share	$ 1.47	$ 1.19