Summary of Significant Accounting Policies (Details 4) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net income loss available to common stockholders
Net income	$ 8,499	$ 41,317	$ 17,212	$ 94,408
Net income applicable to preferred stock	841	7,691	1,708	17,692
Net income applicable to common stock	7,658	33,626	15,504	76,716
Determination of shares:
Weighted-average common shares outstanding (in shares)	78,510,000	78,635,000	78,297,000	78,169,000
Assumed conversion of dilutive employee stock-based awards (in shares)	1,832,000	2,929,000	1,998,000	3,020,000
Assumed conversion of restricted stock (in shares)	51,000	111,000	82,000	101,000
Diluted weighted-average common shares outstanding before participating security	80,393,000	81,675,000	80,377,000	81,290,000
Assumed conversion of preferred stock (in shares)	8,624,000	21,767,000	8,624,000	21,817,000
Diluted weighted-average common shares outstanding (in shares)	89,017,000	103,442,000	89,001,000	103,107,000
Anti-dilutive securities, options to purchase shares outstanding	954,709	20,625	935,147	30,625
Calculation of basic EPS:
Net income applicable to common stock	7,658	33,626	15,504	76,716
Weighted-average common shares outstanding (in shares)	78,510,000	78,635,000	78,297,000	78,169,000
Basic earnings (loss) per common share (in dollars per share)	$ 0.10	$ 0.43	$ 0.20	$ 0.98
Calculation of diluted EPS:
Net income applicable to common stock	7,658	33,626	15,504	76,716
Net income	$ 8,499	$ 41,317	$ 17,212	$ 94,408
Weighted Average Number of Diluted Shares Outstanding Before Participating Security	80,393,000	81,675,000	80,377,000	81,290,000
Diluted weighted-average common shares outstanding	89,017,000	103,442,000	89,001,000	103,107,000
Diluted earnings (loss) per common share (in dollars per share)	$ 0.10	$ 0.40	$ 0.19	$ 0.92
Series C Preferred Stock
Earnings Per Share
Preferred stock , shares outstanding	8,624		8,624
Series B Preferred Stock
Earnings Per Share
Preferred stock , shares outstanding		12,050		12,050