Basic and Diluted Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss) applicable to common shares	$ (202,096)	$ 14,859	$ (271,693)	$ 35,135
Weighted average number of common shares outstanding	157,143	155,918	156,842	155,698
Effect of dilutive stock awards and convertible preferred stock	0	869	0	917
Effect of convertible preferred stock	0	6,065	0	6,065
Weighted average number of diluted common shares outstanding	157,143	162,852	156,842	162,680
Basic net income (loss) per share	$ (1.29)	$ 0.10	$ (1.73)	$ 0.23
Diluted net income (loss) per share	$ (1.29)	$ 0.09	$ (1.73)	$ 0.22
Series D Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Income impact of assumed Series D Preferred Stock conversion	0	338	0	1,014
Net income (loss) after assumed Series D Preferred Stock conversion	$ (202,096)	$ 15,197	$ (271,693)	$ 36,149