Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	The September 2019 Offering [Member] Underwriters' Designees [Member] Common Stock [Member]	The September 2019 Offering [Member] Underwriters' Designees [Member] Additional Paid-in Capital [Member]	The September 2019 Offering [Member] Underwriters' Designees [Member] Retained Earnings [Member]	The September 2019 Offering [Member] Underwriters' Designees [Member]	The September 2019 Offering [Member] Common Stock [Member]	The September 2019 Offering [Member] Additional Paid-in Capital [Member]	The September 2019 Offering [Member] Retained Earnings [Member]	The September 2019 Offering [Member]	The April 2019 Offering [Member] Underwriters' Designees [Member] Common Stock [Member]	The April 2019 Offering [Member] Underwriters' Designees [Member] Additional Paid-in Capital [Member]	The April 2019 Offering [Member] Underwriters' Designees [Member] Retained Earnings [Member]	The April 2019 Offering [Member] Underwriters' Designees [Member]	The April 2019 Offering [Member] Common Stock [Member]	The April 2019 Offering [Member] Additional Paid-in Capital [Member]	The April 2019 Offering [Member] Retained Earnings [Member]	The April 2019 Offering [Member]	Placement Agents' Designees [Member] Common Stock [Member]	Placement Agents' Designees [Member] Additional Paid-in Capital [Member]	Placement Agents' Designees [Member] Retained Earnings [Member]	Placement Agents' Designees [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Common Stock [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balances (in shares) at Dec. 31, 2018																									7,141,189				7,141,189
Balances at Dec. 31, 2018																							$ (27)	$ (27)	$ 1	$ 109,226	$ (98,016)	$ 11,211	$ 1	$ 109,226	$ (97,989)	$ 11,238
Issuance of common stock, net of offering costs (in shares)																													1,200,000
Issuance of common stock, net of offering costs																														2,440		2,440
Issuance of common stock upon exercise of common stock warrants																													1	1,082		$ 1,083
Issuance of common stock upon exercise of stock options (in shares)																																0
Stock-based compensation																														490		$ 490
Net loss																															(12,236)	(12,236)
Issuance of common stock and common stock warrants, net of offering costs (in shares)					26,124,828								925,455
Issuance of common stock and common stock warrants, net of offering costs					$ 3	$ 7,241		$ 7,244						$ 7,741		$ 7,741
Issuance of common stock warrants to placement agents’ designees		$ 497		$ 497						$ 333		$ 333						$ 100		$ 100
Issuance of common stock upon exercise of pre-funded warrants (in shares)																													10,832,122
Balances (in shares) at Sep. 30, 2019																													46,223,594
Balances at Sep. 30, 2019																													$ 5	129,150	(110,252)	18,903
Balances (in shares) at Jun. 30, 2019																													15,785,735
Balances at Jun. 30, 2019																													$ 2	120,835	(104,992)	15,845
Issuance of common stock upon exercise of common stock warrants																														431		431
Stock-based compensation																														146		146
Net loss																															(5,260)	(5,260)
Issuance of common stock and common stock warrants, net of offering costs (in shares)					26,124,828
Issuance of common stock and common stock warrants, net of offering costs					$ 3	$ 7,241		$ 7,244
Issuance of common stock warrants to placement agents’ designees		$ 497		$ 497
Issuance of common stock upon exercise of pre-funded warrants (in shares)																													4,313,031
Balances (in shares) at Sep. 30, 2019																													46,223,594
Balances at Sep. 30, 2019																													$ 5	129,150	(110,252)	18,903
Balances (in shares) at Dec. 31, 2019																													48,254,994
Balances at Dec. 31, 2019																													$ 5	129,608	(116,661)	12,952
Issuance of common stock, net of offering costs (in shares)																													12,503,806
Issuance of common stock, net of offering costs																													$ 1	97,033		97,034
Issuance of common stock upon exercise of common stock warrants (in shares)																													44,404,966
Issuance of common stock upon exercise of common stock warrants																													$ 5	25,946		$ 25,951
Issuance of common stock upon exercise of stock options (in shares)																													305,179			305,179
Issuance of common stock upon exercise of stock options																														402		$ 402
Stock-based compensation																														3,871		3,871
Net loss																															(18,359)	(18,359)
Issuance of common stock and common stock warrants, net of offering costs (in shares)																													4,000,000
Issuance of common stock and common stock warrants, net of offering costs																														8,722		8,722
Issuance of common stock warrants to placement agents’ designees																		$ 453		$ 453
Disgorgement of short-swing profits, net of costs																														652		652
Balances (in shares) at Sep. 30, 2020																													109,468,945
Balances at Sep. 30, 2020																													$ 11	266,687	(135,020)	131,678
Balances (in shares) at Jun. 30, 2020																													96,140,661
Balances at Jun. 30, 2020																													$ 10	167,160	(126,935)	40,235
Issuance of common stock, net of offering costs (in shares)																													12,503,806
Issuance of common stock, net of offering costs																													$ 1	97,033		97,034
Issuance of common stock upon exercise of common stock warrants (in shares)																													697,680
Issuance of common stock upon exercise of common stock warrants																														1,293		1,293
Issuance of common stock upon exercise of stock options (in shares)																													126,798
Issuance of common stock upon exercise of stock options																														286		286
Stock-based compensation																														915		915
Net loss																															(8,085)	(8,085)
Balances (in shares) at Sep. 30, 2020																													109,468,945
Balances at Sep. 30, 2020																													$ 11	$ 266,687	$ (135,020)	$ 131,678