Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	July Public Offering [Member] Preferred Stock [Member]	July Public Offering [Member] Common Stock [Member]	July Public Offering [Member] Additional Paid-in Capital [Member]	July Public Offering [Member] Retained Earnings [Member]	July Public Offering [Member]	August Public Offering [Member] Preferred Stock [Member]	August Public Offering [Member] Common Stock [Member]	August Public Offering [Member] Additional Paid-in Capital [Member]	August Public Offering [Member] Retained Earnings [Member]	August Public Offering [Member]	Series B Preferred Stock [Member] Preferred Stock [Member]	Series B Preferred Stock [Member] Common Stock [Member]	Series B Preferred Stock [Member] Additional Paid-in Capital [Member]	Series B Preferred Stock [Member] Retained Earnings [Member]	Series B Preferred Stock [Member]	Series C Preferred Stock [Member] Preferred Stock [Member]	Series C Preferred Stock [Member] Common Stock [Member]	Series C Preferred Stock [Member] Additional Paid-in Capital [Member]	Series C Preferred Stock [Member] Retained Earnings [Member]	Series C Preferred Stock [Member]	Conversion of Series B Preferred Stock into Common Stock [Member] Preferred Stock [Member]	Conversion of Series B Preferred Stock into Common Stock [Member] Common Stock [Member]	Conversion of Series B Preferred Stock into Common Stock [Member] Additional Paid-in Capital [Member]	Conversion of Series B Preferred Stock into Common Stock [Member] Retained Earnings [Member]	Conversion of Series B Preferred Stock into Common Stock [Member]	Conversion of Series C Preferred Stock into Common Stock [Member] Preferred Stock [Member]	Conversion of Series C Preferred Stock into Common Stock [Member] Common Stock [Member]	Conversion of Series C Preferred Stock into Common Stock [Member] Additional Paid-in Capital [Member]	Conversion of Series C Preferred Stock into Common Stock [Member] Retained Earnings [Member]	Conversion of Series C Preferred Stock into Common Stock [Member]	Conversion of CRG into Series A Preferred Stock [Member] Preferred Stock [Member]	Conversion of CRG into Series A Preferred Stock [Member] Common Stock [Member]	Conversion of CRG into Series A Preferred Stock [Member] Additional Paid-in Capital [Member]	Conversion of CRG into Series A Preferred Stock [Member] Retained Earnings [Member]	Conversion of CRG into Series A Preferred Stock [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2017																																					83,359
Balance at Dec. 31, 2017																																					$ 1	$ 265,636	$ (301,327)	$ (35,690)
Issuance of common stock under officers’ and directors’ purchase plan (in shares)																																					4,401
Issuance of common stock under officers’ and directors’ purchase plan																																						21		21
Employee stock-based compensation																																						3,080		3,080
Exercises of warrants for common stock (in shares)																																					29,050
Exercises of warrants for common stock																																						581		581
Common stock issued to a vendor (in shares)																																					8,000
Common stock issued to a vendor																																						106		106
Issuance of stock (in shares)		216,618									17,979					8,586	728,500
Issuance of stock			$ 3,026		$ 3,026								$ 15,525		$ 15,525			$ 10,179		$ 10,179
Conversion of convertible securities (in shares)																					(16,278)	813,914				(6,416)	1,604,000				41,800
Conversion of convertible securities																											$ 2	$ (2)					$ 42,794		$ 42,794
Issuance of common stock to Lincoln Park (in shares)																																					4,358
Issuance of common stock to Lincoln Park																																						314		314
Accretion of Series A preferred stock dividends																																						(2,918)		(2,918)
Net and comprehensive loss																																							(27,558)	(27,558)
Balance (in shares) at Dec. 31, 2018																																				45,671	3,492,200
Balance at Dec. 31, 2018																																					$ 3	338,342	(328,885)	9,460
Issuance of common stock under officers’ and directors’ purchase plan (in shares)																																					36,087
Issuance of common stock under officers’ and directors’ purchase plan																																						72		72
Employee stock-based compensation																																						2,091		2,091
Exercises of warrants for common stock (in shares)																																					1,998,079
Exercises of warrants for common stock																																					$ 2	7,991		7,993
Issuance of stock (in shares)							3,813,559
Issuance of stock							$ 4	$ 3,807		$ 3,811
Conversion of convertible securities (in shares)																					(1,523)	380,750				(2,170)	542,500
Conversion of convertible securities																											$ 1	$ (1)
Accretion of Series A preferred stock dividends																																						(3,580)		(3,580)
Net and comprehensive loss																																							(19,450)	(19,450)
Issuance of common stock upon vesting of restricted stock units (in shares)																																					101,488
Issuance of common stock upon vesting of restricted stock units
Issuance of Series A preferred stock to pay dividends (in shares)																																				6,525
Issuance of Series A preferred stock to pay dividends																																						6,498		6,498
Balance (in shares) at Dec. 31, 2019																																				48,503	10,364,663
Balance at Dec. 31, 2019																																					$ 10	$ 355,220	$ (348,335)	$ 6,895