STATEMENTS OF CHANGES IN PREFERRED STOCK AND STOCKHOLDERS' Equity (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital Common Stock	Accumulated Deficit	Series 1 Preferred Stock - Mezzanine
Balance at Dec. 31, 2017	$ (96,806)	$ 143	$ 615,493	$ (712,442)	$ 143,992
Balance (in shares) at Dec. 31, 2017		142,658,037			119,644
Adjustment for implementation of ASU No. 2014-09, Revenue from contracts with customers	(8,131)			(8,131)
Stock-based compensation	6,850		6,850
Exercise of employee stock options	240		240
Exercise of employee stock options (in shares)		104,166
Cancelled restricted common stock (in shares)		(70,867)
Repurchase of restricted common stock	(1,275)	$ (1)	(1,274)
Repurchase of restricted common stock (Shares)		(311,566)
Preferred stock dividends			(16,656)		$ 16,437
Preferred stock dividends	(16,656)
Preferred stock dividends (in shares)					11,205
Net loss	(40,636)			(40,636)
Balance at Sep. 30, 2018	(156,414)	$ 142	604,653	(761,209)	$ 160,429
Balance (in shares) at Sep. 30, 2018		142,379,770			130,849
Balance at Jun. 30, 2018	(139,235)	$ 142	609,247	(748,624)	$ 154,428
Balance (in shares) at Jun. 30, 2018		142,379,770			127,002
Stock-based compensation	1,480		1,480
Preferred stock dividends			(6,074)		$ 6,001
Preferred stock dividends	(6,074)
Preferred stock dividends (in shares)					3,847
Net loss	(12,585)			(12,585)
Balance at Sep. 30, 2018	(156,414)	$ 142	604,653	(761,209)	$ 160,429
Balance (in shares) at Sep. 30, 2018		142,379,770			130,849
Balance at Dec. 31, 2018	85,564	$ 161	651,732	(566,329)
Balance (in shares) at Dec. 31, 2018		161,066,136
Stock-based compensation	4,741		4,741
Exercise of employee stock options	$ 1,020		1,020
Exercise of employee stock options (in shares)	482,500	352,652
Restricted stock awards	$ 1,000	$ 1	999
Restricted stock awards (in shares)		1,408,536
Issuance of common stock upon exercise of warrants, net	52,499	$ 18	52,481
Issuance of common stock upon exercise of warrants, net (in shares)		17,803,031
Issuance of inducement warrants	60,751		60,751
Cancelled restricted common stock (in shares)		(74,599)
Restricted stock buy-back at vesting to cover taxes	(370)		(370)
Restricted stock buy-back at vesting to cover taxes (in shares)		(165,178)
Issuance of common stock in connection with at the market offering, net	2,971	$ 1	2,970
Issuance of common stock in connection with at the market offering, net (in shares)		639,442
Net loss	(102,050)			(102,050)
Balance at Sep. 30, 2019	106,126	$ 181	774,324	(668,379)
Balance (in shares) at Sep. 30, 2019		181,030,020
Balance at Jun. 30, 2019	61,995	$ 162	656,216	(594,383)
Balance (in shares) at Jun. 30, 2019		162,477,963
Stock-based compensation	1,486		1,486
Exercise of employee stock options	420		420
Exercise of employee stock options (in shares)		94,584
Restricted stock awards (in shares)		15,000
Issuance of common stock upon exercise of warrants, net	52,499	$ 18	52,481
Issuance of common stock upon exercise of warrants, net (in shares)		17,803,031
Issuance of inducement warrants	60,751		60,751
Issuance of common stock in connection with at the market offering, net	2,971	$ 1	2,970
Issuance of common stock in connection with at the market offering, net (in shares)		639,442
Net loss	(73,996)			(73,996)
Balance at Sep. 30, 2019	$ 106,126	$ 181	$ 774,324	$ (668,379)
Balance (in shares) at Sep. 30, 2019		181,030,020