Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2012 Shares that would be added to EPS calculation if the Company had generated net income	Jun. 30, 2013 Stock options and other stock awards	Jun. 30, 2012 Stock options and other stock awards	Jun. 30, 2013 Stock options and other stock awards	Jun. 30, 2012 Stock options and other stock awards	Jun. 30, 2013 4.25% Convertible Senior Notes	Dec. 31, 2012 4.25% Convertible Senior Notes	Jun. 30, 2012 4.25% Convertible Senior Notes	Jun. 30, 2013 4.25% Convertible Senior Notes	Jun. 30, 2012 4.25% Convertible Senior Notes
Earnings Per Share [Abstract]
Net income (loss)	$ 31,100	$ 5,508	$ 33,477	$ (5,634)
Weighted average common shares outstanding (used to calculate basic EPS) (in shares)	46,481,000	45,945,000	46,426,000	45,892,000
Dilutive effect of stock options and other stock awards (in shares)	835,000	279,000	769,000	0
Weighted average common shares outstanding (used to calculate diluted EPS) (in shares)	47,316,000	46,224,000	47,195,000	45,892,000
Earnings (loss) per common share - basic (in dollars per share)	$ 0.67	$ 0.12	$ 0.72	$ (0.12)
Earnings (loss) per common share - diluted (in dollars per share)	$ 0.66	$ 0.12	$ 0.71	$ (0.12)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of earnings per share, amount (in shares)					500,000	1,700,000	2,600,000	1,800,000	2,000,000
Stated interest rate on debt instrument										4.25%	4.25%	4.25%	4.25%	4.25%
Conversion price (in dollars per share)										$ 22.45			$ 22.45	$ 22.45