Net Income Per Common Share- Calculation of Basic Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Numerator for basic net (loss) income per share:
Net income (loss)	$ (16,645)	$ (3,919)	$ 61,314	$ (71,901)	$ (61,833)
Less: Series B preferred stock dividends	4,500	4,500	13,500	13,248
Less: undistributed earnings attributed to participating securities (basic calculation)			27,625
Basic net (loss) income attributable to common stockholders	$ (21,145)	$ (8,419)	$ 20,189	$ (85,149)
Denominator for basic net (loss) income per share:
Weighted-average shares outstanding	206,380,800	206,168,035	206,261,993	204,307,431
Weighted-average unvested restricted shares outstanding	(4,039,591)	(4,197,396)	(4,014,718)	(2,636,314)
Denominator for basic net (loss) income per share	202,341,209	201,970,639	202,247,275	201,671,117
Basic net (loss) income per share attributable to common stockholders	$ (0.10)	$ (0.04)	$ 0.10	$ (0.42)