Net (Loss) Income Per Share - Computation of Basic and Dilutive Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net (loss) income	$ (36,224)	$ (178)	$ 1,804	$ 4,619	$ 4,276	$ 44,051	$ 10,402	$ 5,998	$ (29,979)	$ 64,727	$ 390
Denominator for basic earnings (loss) per share - weighted average shares (in shares)									105,596,256	106,121,810	105,928,348
Effect of dilutive securities: Stock options, warrants, and restricted stock (in shares)									3,538,921	9,991,926	6,717,292
Denominator for diluted earnings (loss) per share - weighted average shares adjusted for dilutive securities (in shares)									105,596,256	116,113,736	112,645,640
(Loss) income per common share - basic (in dollars per share)	$ (0.34)	$ 0	$ 0.02	$ 0.04	$ 0.04	$ 0.41	$ 0.10	$ 0.06	$ (0.28)	$ 0.61	$ 0.00
(Loss) income per common share - diluted (in dollars per share)	$ (0.34)	$ 0	$ 0.02	$ 0.04	$ 0.04	$ 0.37	$ 0.09	$ 0.05	$ (0.28)	$ 0.56	$ 0