Condensed Consolidated Statements of Stockholders' Equity / (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Purchase Agreement	Purchase Agreement Common Stock	Purchase Agreement Additional Paid-in Capital	Second Purchase Agreement	Second Purchase Agreement Common Stock	Second Purchase Agreement Additional Paid-in Capital	Series A Preferred Stock	Series B Preferred Stock
Beginning balance at Dec. 31, 2017	$ (4,058)	$ 0	$ (24)	$ 469,884	$ (473,921)							$ 3	$ 0
Beginning balance (shares) at Dec. 31, 2017		350,118	392									2,750,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,029			1,029
Restricted stock vested (shares)		1,500
Issuance of common stock as a result of Employee Stock Purchase Program	137			137
Issuance of common stock as a result of Employee Stock Purchase Program (shares)		2,755
Net loss	(11,574)				(11,574)
Ending balance at Mar. 31, 2018	(14,487)	$ 0	$ (24)	471,050	(485,516)							$ 3	$ 0
Ending balance (shares) at Mar. 31, 2018		354,373	392									2,750,000	0
Beginning balance at Dec. 31, 2017	(4,058)	$ 0	$ (24)	469,884	(473,921)							$ 3	$ 0
Beginning balance (shares) at Dec. 31, 2017		350,118	392									2,750,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(34,065)
Ending balance at Sep. 30, 2018	(7,383)	$ 1	$ (24)	500,644	(508,007)							$ 3	$ 0
Ending balance (shares) at Sep. 30, 2018		1,247,261	392									2,750,000	0
Beginning balance at Mar. 31, 2018	(14,487)	$ 0	$ (24)	471,050	(485,516)							$ 3	$ 0
Beginning balance (shares) at Mar. 31, 2018		354,373	392									2,750,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,011			1,011
Issuance of common stock as a result of Purchase Agreements, net of fees						$ 2,885		$ 2,885
Issuance of common stock as a result of Purchase Agreements, net of fees (shares)							102,121			13,193
Issuance of common stock through sales agreement, net of fees	24,359	$ 1		24,358
Issuance of common stock through sales agreement, net of fees (shares)		765,000
Net loss	(10,960)				(10,960)
Ending balance at Jun. 30, 2018	2,808	$ 1	$ (24)	499,304	(496,476)							$ 3	$ 0
Ending balance (shares) at Jun. 30, 2018		1,234,687	392.000									2,750,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,020			1,020
Issuance of common stock as a result of Purchase Agreements, net of fees						221		221
Issuance of common stock as a result of Purchase Agreements, net of fees (shares)							7,500
Issuance of common stock through sales agreement, net of fees	99			99
Issuance of common stock through sales agreement, net of fees (shares)		5,074
Net loss	(11,531)				(11,531)
Ending balance at Sep. 30, 2018	(7,383)	$ 1	$ (24)	500,644	(508,007)							$ 3	$ 0
Ending balance (shares) at Sep. 30, 2018		1,247,261	392									2,750,000	0
Beginning balance at Dec. 31, 2018	14,289	$ 5	$ (24)	534,176	(519,871)							$ 3	$ 0
Beginning balance (shares) at Dec. 31, 2018		4,997,151.55	392									2,750,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,069			1,069
Issuance of common stock through sales agreement, net of fees	773	$ 0		773
Issuance of common stock through sales agreement, net of fees (shares)		109,117
Issuance of common stock with exercise of Series B warrants	20	$ 0		20
Issuance of preferred stock upon conversion of debt (shares)		2,096
Net loss	(14,684)				(14,684)
Ending balance at Mar. 31, 2019	1,467	$ 5	$ (24)	536,038	(534,555)							$ 3	$ 0
Ending balance (shares) at Mar. 31, 2019		5,108,365	392									2,750,000	0
Beginning balance at Dec. 31, 2018	14,289	$ 5	$ (24)	534,176	(519,871)							$ 3	$ 0
Beginning balance (shares) at Dec. 31, 2018		4,997,151.55	392									2,750,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(41,947)
Ending balance at Sep. 30, 2019	11,024	$ 8	$ (24)	572,851	(561,831)							$ 3	$ 17
Ending balance (shares) at Sep. 30, 2019		8,271,503	392									2,750,000	17,123,284
Beginning balance at Mar. 31, 2019	1,467	$ 5	$ (24)	536,038	(534,555)							$ 3	$ 0
Beginning balance (shares) at Mar. 31, 2019		5,108,365	392									2,750,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	813			813
Issuance of common stock through sales agreement, net of fees	3,831	$ 1		3,830
Issuance of common stock through sales agreement, net of fees (shares)		879,859
Net loss	(14,019)				(14,019)
Ending balance at Jun. 30, 2019	(7,908)	$ 6	$ (24)	540,681	(548,574)							$ 3	$ 0
Ending balance (shares) at Jun. 30, 2019		5,988,224	392									2,750,000	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	699			699
Issuance of common stock as a result of Purchase Agreements, net of fees						$ 1,915	$ 1	$ 1,914
Issuance of common stock as a result of Purchase Agreements, net of fees (shares)							1,088,100
Issuance of common stock through sales agreement, net of fees									$ 4,562	$ 1	$ 4,561
Issuance of common stock through sales agreement, net of fees (shares)										1,195,179
Issuance of preferred stock upon conversion of debt	25,000			24,983									$ 17
Issuance of preferred stock upon exchange of debt (shares)													17,123,284
Common stock dividends distributable				7	(7)
Series B dividends distributable				6	(6)
Net loss	(13,244)				(13,244)
Ending balance at Sep. 30, 2019	$ 11,024	$ 8	$ (24)	$ 572,851	$ (561,831)							$ 3	$ 17
Ending balance (shares) at Sep. 30, 2019		8,271,503	392									2,750,000	17,123,284