UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Bought Deal	Public Offering	At-the-Market Offering	COMMON STOCK	COMMON STOCK Bought Deal	COMMON STOCK Public Offering	COMMON STOCK At-the-Market Offering	ADDITIONAL PAID-IN CAPITAL	ADDITIONAL PAID-IN CAPITAL Bought Deal	ADDITIONAL PAID-IN CAPITAL Public Offering	ADDITIONAL PAID-IN CAPITAL At-the-Market Offering	ACCUMULATED DEFICIT	ACCUMULATED OTHER COMPREHENSIVE INCOME
Beginning balance (in shares) at Dec. 31, 2019					65,378,890
Beginning balance at Dec. 31, 2019	$ 20,320				$ 7				$ 326,777				$ (306,516)	$ 52
Increase (Decrease) in Shareholders' Equity
Net Loss	(7,984)												(7,984)
Unrealized Gain (Loss) on Available-for-Sale Debt Instrument Investments	(7)													(7)
Foreign Currency Translation Adjustments	6													6
Issuance of common stock, net of offering costs (in shares)						3,670,212
Issuance of common stock, net of offering costs		$ 8,003								$ 8,003
Issuance of Warrants related to Debt Financing	501								501
Stock-based Compensation expense	935								935
Ending balance (in shares) at Mar. 31, 2020					69,049,102
Ending balance at Mar. 31, 2020	21,774				$ 7				336,216				(314,500)	51
Beginning balance (in shares) at Dec. 31, 2019					65,378,890
Beginning balance at Dec. 31, 2019	20,320				$ 7				326,777				(306,516)	52
Increase (Decrease) in Shareholders' Equity
Net Loss	(22,227)
Unrealized Gain (Loss) on Available-for-Sale Debt Instrument Investments	(11)
Foreign Currency Translation Adjustments	8
Ending balance (in shares) at Sep. 30, 2020					93,573,165
Ending balance at Sep. 30, 2020	42,075				$ 9				370,760				(328,743)	49
Beginning balance (in shares) at Mar. 31, 2020					69,049,102
Beginning balance at Mar. 31, 2020	21,774				$ 7				336,216				(314,500)	51
Increase (Decrease) in Shareholders' Equity
Net Loss	(6,893)												(6,893)
Unrealized Gain (Loss) on Available-for-Sale Debt Instrument Investments	(6)													(6)
Foreign Currency Translation Adjustments	1													1
Issuance of common stock, net of offering costs (in shares)								987,716
Issuance of common stock, net of offering costs				$ 1,978								$ 1,978
Vesting of Restricted Stock Units Issued, net of taxes withheld (in shares)					120,104
Vesting of Restricted Stock Units Issued, net of taxes withheld	(19)								(19)
Warrant Modification Expense	837								837
Stock-based Compensation expense	(1,461)								(1,461)
Ending balance (in shares) at Jun. 30, 2020					70,156,922
Ending balance at Jun. 30, 2020	16,211				$ 7				337,551				(321,393)	46
Increase (Decrease) in Shareholders' Equity
Net Loss	(7,350)												(7,350)
Unrealized Gain (Loss) on Available-for-Sale Debt Instrument Investments	2													2
Foreign Currency Translation Adjustments	1													1
Issuance of common stock, net of offering costs (in shares)							23,178,809	140,892
Issuance of common stock, net of offering costs			$ 32,677	$ 284			$ 2				$ 32,675	$ 284
Vesting of Restricted Stock Units Issued, net of taxes withheld (in shares)					96,542
Stock-based Compensation expense	250								250
Ending balance (in shares) at Sep. 30, 2020					93,573,165
Ending balance at Sep. 30, 2020	$ 42,075				$ 9				370,760				(328,743)	49
Beginning balance (in shares) at Dec. 31, 2020	93,573,165				93,573,165
Beginning balance at Dec. 31, 2020	$ 34,170				$ 9				371,510				(337,406)	57
Increase (Decrease) in Shareholders' Equity
Net Loss	(7,752)												(7,752)
Unrealized Gain (Loss) on Available-for-Sale Debt Instrument Investments	(7)													(7)
Foreign Currency Translation Adjustments	3													3
Stock-based Compensation expense (in shares)					26,354
Stock-based Compensation expense	(236)								(236)
Ending balance (in shares) at Mar. 31, 2021					93,599,519
Ending balance at Mar. 31, 2021	$ 26,178				$ 9				371,274				(345,158)	53
Beginning balance (in shares) at Dec. 31, 2020	93,573,165				93,573,165
Beginning balance at Dec. 31, 2020	$ 34,170				$ 9				371,510				(337,406)	57
Increase (Decrease) in Shareholders' Equity
Net Loss	(23,733)
Unrealized Gain (Loss) on Available-for-Sale Debt Instrument Investments	(4)
Foreign Currency Translation Adjustments	$ 3
Ending balance (in shares) at Sep. 30, 2021	93,966,381				93,966,381
Ending balance at Sep. 30, 2021	$ 11,094				$ 9				372,168				(361,139)	56
Beginning balance (in shares) at Mar. 31, 2021					93,599,519
Beginning balance at Mar. 31, 2021	26,178				$ 9				371,274				(345,158)	53
Increase (Decrease) in Shareholders' Equity
Net Loss	(8,400)												(8,400)
Unrealized Gain (Loss) on Available-for-Sale Debt Instrument Investments	(1)													(1)
Vesting of Restricted Stock Units Issued, net of taxes withheld (in shares)					211,862
Vesting of Restricted Stock Units Issued, net of taxes withheld	(7)								(7)
Stock-based Compensation expense	433								433
Ending balance (in shares) at Jun. 30, 2021					93,811,381
Ending balance at Jun. 30, 2021	18,203				$ 9				371,700				(353,558)	52
Increase (Decrease) in Shareholders' Equity
Net Loss	(7,581)												(7,581)
Unrealized Gain (Loss) on Available-for-Sale Debt Instrument Investments	4													4
Foreign Currency Translation Adjustments	0
Issued shares for services (in shares)					155,000
Issued shares for services	107								107
Stock-based Compensation expense	$ 361								361
Ending balance (in shares) at Sep. 30, 2021	93,966,381				93,966,381
Ending balance at Sep. 30, 2021	$ 11,094				$ 9				$ 372,168				$ (361,139)	$ 56