Net Loss per Common Share - Calculation of Net Loss and Number of Shares Used to Compute Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net (loss) income - basic		$ (5,959)	$ (7,894)	$ (6,658)	$ 7,185	$ (13,853)	$ 527
Adjustment for gain on warrant income							(619)
Net loss - diluted						$ (13,853)	$ (92)
Weighted average shares outstanding - basic	[1]	71,303,364		916,706		72,069,390	788,512
Weighted average shares outstanding - diluted	[1]	71,303,364		916,706		72,069,390	799,430
Net loss per share - basic	[1]	$ (0.08)		$ (7.26)		$ (0.19)	$ 0.67
Net loss per share - diluted*	[1]	$ (0.08)		$ (7.26)		$ (0.19)	$ (0.12)

[1] reflects a one-for-five hundred (1:500) reverse stock split effected on May 2, 2018.