STATEMENTS OF CHANGES IN PREFERRED STOCK AND STOCKHOLDERS' Equity (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital	Accumulated Deficit	Series 1 Preferred Stock - Mezzanine
Balance at Dec. 31, 2017	$ (96,806)	$ 143	$ 615,493	$ (712,442)	$ 143,992
Balance (Accounting Standards Update 2014-09 [Member]) at Dec. 31, 2017	(8,131)			(8,131)
Balance (in shares) at Dec. 31, 2017		142,658,037			119,644
Stock-based compensation	7,534		7,534
Issuance of restricted common stock	1	$ 2	(1)
Issuance of restricted common stock (in shares)		150,321
Exercise of employee stock options	$ 242	$ 2	240
Exercise of employee stock options (in shares)	104,167	104,166
Cancelled restricted common stock	$ 1	$ (2)	3
Cancelled restricted common stock (in shares)		(271,433)
Repurchase of restricted common stock	(1,624)	$ (3)	(1,621)
Repurchase of restricted common stock (Shares)		(514,349)
Issuance of common stock in connection with a public offering, net	47,101	$ 19	47,082
Issuance of common stock in connection with a public offering, net (in shares)		18,939,394
Preferred stock dividends	(16,998)		(16,998)		$ (16,775)
Preferred stock dividends (in shares)					11,415
Settlement of a related party relationship (Note 7)	207,361			207,361	$ (160,767)
Settlement of a related party relationship (Note 7) (in shares)					(131,059)
Net loss	(53,117)			(53,117)
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	6,341		6,341
Issuance of restricted common stock	1,000	$ 2	998
Issuance of restricted common stock (in shares)		1,519,766
Exercise of employee stock options	$ 1,219	$ 1,219
Exercise of employee stock options (in shares)	581,105	443,051
Cancelled restricted common stock (in shares)		(74,599)
Issuance of common stock upon exercise of warrants, net	$ 60,751		60,751
Repurchase of restricted common stock	(653)	$ (653)
Repurchase of restricted common stock (Shares)		(225,339)
Issuance of common stock in connection with at the market offering, net	6,085	$ 1	6,084
Issuance of common stock in connection with at the market offering, net (in shares)		1,271,274
Warrant exercise, net of commissions and expenses of $1.1 million	52,499	$ 18	52,481
Warrant exercise, net of commissions and expenses of $1.1 million (in shares)		17,803,031
Net loss	(117,796)			(117,796)
Balance at Dec. 31, 2019	95,010	$ 182	778,953	(684,125)
Balance (in shares) at Dec. 31, 2019		181,803,320
Stock-based compensation	6,829		6,829
Exercise of employee stock options	$ 442		442
Exercise of employee stock options (in shares)	338,333	252,799
Restricted stock awards		$ 1	(1)
Restricted stock awards (in shares)		805,900
Cancelled restricted common stock (in shares)		(194,897)
Issuance of common stock in connection with at the market offering, net	$ 13,016	$ 3	13,013
Issuance of common stock in connection with at the market offering, net (in shares)	2,814,673	2,814,673
Issuance of common stock in connection with a public offering, net	$ 88,661	$ 29	88,632
Issuance of common stock in connection with a public offering, net (in shares)		29,110,111
Net loss	(79,976)			(79,976)
Balance at Dec. 31, 2020	$ 123,982	$ 215	$ 887,868	$ (764,101)
Balance (in shares) at Dec. 31, 2020		214,591,906