Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Basic and Diluted Earnings per share
Weighted average basic common shares outstanding	23,315	21,650	22,796	21,640
Dilutive effect of contingently convertible notes and warrants	1,660	851	1,743	871
Dilutive effect of stock options, net of assumed repurchase of treasury stock	0	4	0	5
Dilutive effect of employee stock purchases, net of assumed repurchase of treasury stock	5	8	5	6
Weighted average dilutive common shares outstanding	24,980	22,513	24,544	22,522
Basic:
Net income	$ 37,388	$ 28,625	$ 59,506	$ 51,742
Less: Earning allocated to participating securities	1,689	1,628	2,684	2,822
Earnings available to basic common shares	35,699	26,997	56,822	48,920
Basic earnings per common share	$ 1.53	$ 1.25	$ 2.49	$ 2.26
Diluted:
Net income	37,388	28,625	59,506	51,742
Less: Earning allocated to participating securities	1,592	1,576	2,522	2,730
Earnings available to diluted common shares	$ 35,796	$ 27,049	$ 56,984	$ 49,012
Diluted earnings per common share	$ 1.43	$ 1.20	$ 2.32	$ 2.18