UNAUDITED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - 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, 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)