Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	December 2018 Offering [Member] Preferred Stock [Member] Series A Preferred Stock [Member]	December 2018 Offering [Member] Preferred Stock [Member] Series B Preferred Stock [Member]	December 2018 Offering [Member] Common Stock [Member]	December 2018 Offering [Member] Additional Paid-in Capital [Member]	December 2018 Offering [Member] Retained Earnings [Member]	December 2018 Offering [Member]	February 2018 Offering [Member] Preferred Stock [Member] Series A Preferred Stock [Member]	February 2018 Offering [Member] Preferred Stock [Member] Series B Preferred Stock [Member]	February 2018 Offering [Member] Common Stock [Member]	February 2018 Offering [Member] Additional Paid-in Capital [Member]	February 2018 Offering [Member] Retained Earnings [Member]	February 2018 Offering [Member]	November 2017 ATM Facility [Member] Preferred Stock [Member] Series A Preferred Stock [Member]	November 2017 ATM Facility [Member] Preferred Stock [Member] Series B Preferred Stock [Member]	November 2017 ATM Facility [Member] Common Stock [Member]	November 2017 ATM Facility [Member] Additional Paid-in Capital [Member]	November 2017 ATM Facility [Member] Retained Earnings [Member]	November 2017 ATM Facility [Member]	August 2019 ATM Facility [Member] Preferred Stock [Member] Series A Preferred Stock [Member]	August 2019 ATM Facility [Member] Preferred Stock [Member] Series B Preferred Stock [Member]	August 2019 ATM Facility [Member] Common Stock [Member]	August 2019 ATM Facility [Member] Additional Paid-in Capital [Member]	August 2019 ATM Facility [Member] Retained Earnings [Member]	August 2019 ATM Facility [Member]	November 2019 Offering [Member] Preferred Stock [Member] Series A Preferred Stock [Member]	November 2019 Offering [Member] Preferred Stock [Member] Series B Preferred Stock [Member]	November 2019 Offering [Member] Common Stock [Member]	November 2019 Offering [Member] Additional Paid-in Capital [Member]	November 2019 Offering [Member] Retained Earnings [Member]	November 2019 Offering [Member]	Preferred Stock [Member] Series A Preferred Stock [Member]	Preferred Stock [Member] Series B Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Series B Preferred Stock [Member]	Total
Balances (in shares) at Dec. 31, 2017																																	195,033
Balances at Dec. 31, 2017																																		$ 102,981	$ (105,581)		$ (2,600)
Stock offering, net of issuance costs (in shares)			147,285						115,000						2,771			2,771
Stock offering, net of issuance costs				$ 20,384		$ 20,384				$ 32,214		$ 32,214				$ 1,193		$ 1,193
Stock-based compensation expense																																		2,699			2,699
Issuance of restricted stock awards to directors, employees and consultants (in shares)																																	1,285
Issuance of restricted stock awards to directors, employees and consultants																																		336			336
Issuance of restricted common shares (in shares)																																	1,000
Issuance of restricted common shares																																		257			257
Issuance of common shares from employee stock purchase plan (in shares)																																	1,256
Issuance of common shares from employee stock purchase plan																																		233			233
Cumulative effect adjustment from adoption of new accounting standard – ASC 606																																			177		177
Net loss																																			(49,981)		(49,981)
Balances (in shares) at Dec. 31, 2018																																	463,630
Balances at Dec. 31, 2018																																		160,297	(155,385)		4,912
Stock offering, net of issuance costs (in shares)																		0			1,004,171			1,004,171	5,473,410		1,945,943
Stock offering, net of issuance costs																						$ 6,322		$ 6,322			$ 1	$ 9,951		$ 9,952
Stock-based compensation expense																																		2,251			2,251
Issuance of restricted stock awards to directors, employees and consultants (in shares)																																	1,169
Issuance of restricted stock awards to directors, employees and consultants																																		74			74
Issuance of restricted common shares (in shares)																																	38,689
Issuance of restricted common shares																																		75			75
Issuance of common shares from employee stock purchase plan (in shares)																																	1,531
Issuance of common shares from employee stock purchase plan																																		56			56
Net loss																																			(42,526)		(42,526)
Conversion of Series A convertible preferred stock into common stock (in shares)																															(3,621,237)
Conversion of Series A convertible preferred stock into common stock
Conversion of Series A convertible preferred stock into common stock (in shares)																																	3,621,237
Issuance of Series B convertible preferred stock and common stock warrants in connection with debt conversion, net of issuance costs (in shares)																																31,300
Issuance of Series B convertible preferred stock and common stock warrants in connection with debt conversion, net of issuance costs																																		35,413			35,413
Series B convertible preferred stock dividends (in shares)																																378,000				378
Series B convertible preferred stock dividends																																		(2)			(2)
Reverse stock split - cancellation and payout of fractional shares (in shares)																																	(686)
Reverse stock split - cancellation and payout of fractional shares																																		(6)			(6)
Balances (in shares) at Dec. 31, 2019																															1,852,173	31,678	7,075,684
Balances at Dec. 31, 2019																																	$ 1	$ 214,431	$ (197,911)		$ 16,521