Net Loss Per Common Share - Basic Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net loss	$ (16,580)	$ (19,417)	$ (8,466)	$ (4,821)	$ (7,476)	$ 12,379	$ (17,210)	$ (13,273)	$ (49,284)	$ (25,580)	$ (29,979)
Adjustments to reconcile to net loss available to common stockholders:
Accumulated dividend on Series B Convertible Preferred Stock									2,016	0	0
Amortization of beneficial conversion feature									31,110	0	0
Accretion of increasing-rate dividend feature									918	0	0
Total adjustments									34,044	0	0
Net loss available to common stockholders									$ (83,328)	$ (25,580)	$ (29,979)
Weighted average shares outstanding - basic (in shares)									108,257,112	106,946,384	105,596,256
Basic net (loss) income per common share (in dollars per share)	$ (0.17)	$ (0.48)	$ (0.08)	$ (0.04)	$ (0.07)	$ 0.12	$ (0.16)	$ (0.12)	$ (0.77)	$ (0.24)	$ (0.28)