Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	The July 2020 Offering [Member] Common Stock [Member]	The July 2020 Offering [Member] Additional Paid-in Capital [Member]	The July 2020 Offering [Member] Retained Earnings [Member]	The July 2020 Offering [Member]	The March 2020 Offering [Member] Common Stock [Member]	The March 2020 Offering [Member] Additional Paid-in Capital [Member]	The March 2020 Offering [Member] Retained Earnings [Member]	The March 2020 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]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
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 (in shares)	12,503,806				4,000,000
Issuance of common stock	$ 1	$ 97,033	$ 0	$ 97,034	$ 0	$ 8,722	$ 0	$ 8,722
Issuance of common stock upon exercise of stock options (in shares)													305,179				305,179
Issuance of common stock upon exercise of stock options													$ 0	402	0		$ 402
Stock-based compensation													0	3,871	0		3,871
Net loss													$ 0	0	(18,359)		(18,359)
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	0		25,951
Issuance of common stock warrants to placement agents’ designees									$ 0	$ 453	$ 0	$ 453
Disgorgement of short-swing profits, net of costs													$ 0	652	0		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 (in shares)	12,503,806
Issuance of common stock	$ 1	$ 97,033	$ 0	$ 97,034
Issuance of common stock upon exercise of stock options (in shares)													126,798
Issuance of common stock upon exercise of stock options													$ 0	286	0		286
Stock-based compensation													0	915	0		915
Net loss													$ 0	0	(8,085)		(8,085)
Issuance of common stock upon exercise of common stock warrants (in shares)													697,680
Issuance of common stock upon exercise of common stock warrants													$ 0	1,293	0		1,293
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 Sep. 30, 2021													125,294,816
Balances at Sep. 30, 2021													$ 13	403,525	(198,587)	$ (3)	204,948
Balances (in shares) at Dec. 31, 2020													110,271,093
Balances at Dec. 31, 2020													$ 11	272,274	(148,881)	0	123,404
Issuance of common stock (in shares)													13,239,839
Issuance of common stock													$ 2	122,208	0	0	$ 122,210
Issuance of common stock upon exercise of stock options (in shares)													771,344				771,344
Issuance of common stock upon exercise of stock options													$ 0	1,240	0	0	$ 1,240
Stock-based compensation													0	5,954	0	0	5,954
Unrealized gains (losses) on available-for-sale investments													0	0	0	(3)	(3)
Net loss													$ 0	0	(49,706)	0	(49,706)
Issuance of common stock upon exercise of common stock warrants (in shares)													1,012,540
Issuance of common stock upon exercise of common stock warrants													$ 0	1,849	0	0	1,849
Balances (in shares) at Sep. 30, 2021													125,294,816
Balances at Sep. 30, 2021													$ 13	403,525	(198,587)	(3)	204,948
Balances (in shares) at Jun. 30, 2021													122,814,467
Balances at Jun. 30, 2021													$ 12	380,783	(181,004)	(9)	199,782
Issuance of common stock (in shares)													2,280,931
Issuance of common stock													$ 1	20,295	0	0	20,296
Issuance of common stock upon exercise of stock options (in shares)													199,418
Issuance of common stock upon exercise of stock options													$ 0	348	0	0	348
Stock-based compensation													0	2,099	0	0	2,099
Unrealized gains (losses) on available-for-sale investments													0	0	0	6	6
Net loss													$ 0	0	(17,583)	0	(17,583)
Balances (in shares) at Sep. 30, 2021													125,294,816
Balances at Sep. 30, 2021													$ 13	$ 403,525	$ (198,587)	$ (3)	$ 204,948