Summary of Significant Accounting Policies (Details 6) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income loss available to common stockholders
Net income	$ (9,066)	$ 4,900	$ 2,983	$ 1,869	$ (149,781)	$ (15,348)	$ (19,273)	$ 580	$ 686	$ (183,822)	$ (581,252)
Net income applicable to preferred stock									67
Net income applicable to common stock									$ 619
Determination of shares:
Weighted-average common shares outstanding									80,003,000	78,425,000	78,111,000
Assumed conversion of dilutive employee stock-based awards (in shares)									2,217,000
Assumed conversion of restricted stock (in shares)									60,000
Diluted weighted-average common shares outstanding before participating security									82,280,000
Assumed conversion of preferred stock (in shares)									8,624,000
Diluted weighted-average common shares outstanding (in shares)									90,904,000	78,425,000	78,111,000
Anti-dilutive securities, options to purchase shares outstanding									1,635,929	6,633,622	7,316,713
Calculation of basic EPS:
Net income applicable to common stock									$ 619
Weighted-average common shares outstanding									80,003,000	78,425,000	78,111,000
Basic EPS (in dollars per share)	$ (0.11)	$ 0.06	$ 0.03	$ 0.02					$ 0.01	$ (2.34)	$ (7.44)
Calculation of diluted EPS using two class method:
Net income applicable to common stock									$ 619
Diluted weighted-average common shares outstanding before participating security									82,280,000
Diluted EPS (in dollars per share)	$ (0.11)	$ 0.05	$ 0.03	$ 0.02					$ 0.01	$ (2.34)	$ (7.44)
Series C Preferred Stock
Earnings Per Share
Preferred stock, shares outstanding	8,624				8,624				8,624	8,624	8,624
Series B Preferred Stock
Earnings Per Share
Preferred stock, shares outstanding	0				0				0	0		12,275