UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ DEFICIT - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Equity, beginning balance at Dec. 31, 2017	$ (84,752)	$ 0	$ 13	$ (16)	$ 624,762	$ (709,511)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, vesting of restricted stock and related tax withholdings	(297)			(338)	41
Accrued dividends on preferred stock	(2,657)				(2,657)
Stock-based compensation	511				511
Net loss	(13,017)					(13,017)
Equity, ending balance at Mar. 31, 2018	(100,212)	0	13	(354)	622,657	(722,528)
Equity, beginning balance at Dec. 31, 2017	(84,752)	0	13	(16)	624,762	(709,511)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(28,156)
Equity, ending balance at Jun. 30, 2018	(116,966)		13	(327)	621,015	(737,667)
Equity, beginning balance at Mar. 31, 2018	(100,212)	0	13	(354)	622,657	(722,528)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, vesting of restricted stock and related tax withholdings	121			27	94
Accrued dividends on preferred stock	(2,756)				(2,756)
Stock-based compensation	1,020				1,020
Net loss	(15,139)					(15,139)
Equity, ending balance at Jun. 30, 2018	(116,966)		13	(327)	621,015	(737,667)
Equity, beginning balance at Dec. 31, 2018	(144,004)	0	13	(950)	618,137	(761,204)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, vesting of restricted stock and related tax withholdings	(133)			(386)	253
Accrued dividends on preferred stock	(2,957)				(2,957)
Stock-based compensation	1,034				1,034
Net loss	(10,282)					(10,282)
Equity, ending balance at Mar. 31, 2019	(156,342)	0	13	(1,336)	616,467	(771,486)
Equity, beginning balance at Dec. 31, 2018	(144,004)	0	13	(950)	618,137	(761,204)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(25,948)
Equity, ending balance at Jun. 30, 2019	(174,526)	0	13	(1,722)	614,335	(787,152)
Equity, beginning balance at Mar. 31, 2019	(156,342)	0	13	(1,336)	616,467	(771,486)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, vesting of restricted stock and related tax withholdings	(386)			(386)	0
Accrued dividends on preferred stock	(3,068)				(3,068)
Stock-based compensation	936				936
Net loss	(15,666)					(15,666)
Equity, ending balance at Jun. 30, 2019	$ (174,526)	$ 0	$ 13	$ (1,722)	$ 614,335	$ (787,152)