Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share [Abstract]
Net income (loss)	$ (66,754)	$ (28,826)	$ (72,388)	$ 73,151
Weighted average common shares outstanding (used to calculate basic EPS) (in shares)	46,141,000	45,637,000	45,975,000	45,463,000
Dilutive effect of stock awards (in shares)	0	0	0	796,000
Weighted average common shares outstanding (used to calculate diluted EPS) (in shares)	46,141,000	45,637,000	45,975,000	46,259,000
Earnings (loss) per common share - basic (in dollars per share)	$ (1.45)	$ (0.63)	$ (1.57)	$ 1.61
Earnings (loss) per common share - diluted (in dollars per share)	$ (1.45)	$ (0.63)	$ (1.57)	$ 1.58
Additional shares used to calculated diluted EPS, if income (in shares)	400,000	600,000	500,000
Stated interest rate on debt instrument	4.25%	4.25%	4.25%	4.25%
Conversion price on Convertible Senior Notes due 2016 (in dollars per share)	$ 22.45	$ 22.45	$ 22.45	$ 22.45
Antidilutive shares excluded from computation of earnings per share, amount (in shares)	1,600,000	1,900,000	1,900,000	1,200,000