Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock Public offering	Common Stock At-the-market sales	Common Stock	Additional Paid-in Capital Public offering	Additional Paid-in Capital At-the-market sales	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Public offering	At-the-market sales	Total
Balance at Dec. 31, 2019			$ 7			$ 306,108		$ (260,370)			$ 45,745
Balance (in shares) at Dec. 31, 2019			69,810,305
Increase (decrease) in stockholders' equity
Share-based compensation - stock options and RSUs						621					621
Issuance of common stock	$ 2			$ 48,433					$ 48,435
Issuance of common stock (in shares)	17,250,000
Issuance of common stock upon exercise of options						119					119
Issuance of common stock upon exercise of options (in shares)			152,907
Warrants issued in connection with long-term debt						3,570					3,570
Net loss								(7,883)			(7,883)
Balance at Mar. 31, 2020			$ 9			358,851		(268,253)			90,607
Balance (in shares) at Mar. 31, 2020			87,213,212
Balance at Dec. 31, 2020			$ 9			361,539	$ 3	(312,223)			49,328
Balance (in shares) at Dec. 31, 2020			87,563,753
Increase (decrease) in stockholders' equity
Share-based compensation - stock options and RSUs						742					742
Issuance of common stock					$ 960					$ 960
Issuance of common stock (in shares)		520,937
Issuance of common stock upon exercise of options						75					75
Issuance of common stock upon exercise of options (in shares)			126,400
Vesting of RSUs (in shares)			52,651
Warrants issued in connection with long-term debt						1,080					1,080
Unrealized net gain on marketable securities							$ (3)				(3)
Net loss								(17,128)			(17,128)
Balance at Mar. 31, 2021			$ 9			$ 364,396		$ (329,351)			$ 35,054
Balance (in shares) at Mar. 31, 2021			88,263,741