Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common stock Public offering	Common stock Private Placement	Common stock At-the-market sales	Common stock	Additional Paid in Capital. Public offering	Additional Paid in Capital. Private Placement	Additional Paid in Capital. At-the-market sales	Additional Paid in Capital. Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Additional Paid in Capital.	Accumulated Other Comprehensive Income Public offering	Accumulated Other Comprehensive Income	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjusted Balance [Member]	Accumulated Deficit	Public offering	Private Placement	At-the-market sales	Total
Balance at Dec. 31, 2018				$ 3					$ 261,722				$ (241,551)				$ 20,174
Balance (in shares) at Dec. 31, 2018				34,377,329
Increase (decrease) in stockholders' equity
Share-based compensation - stock options and RSUs									1,762								1,762
Issuance of common stock	$ 2	$ 1	$ 1		$ 12,685	$ 7,809	$ 21,753							$ 12,687	$ 7,810	$ 21,754
Issuance of common stock (in shares)	14,526,315	8,426,750	12,242,436
Issuance of common stock upon exercise of options									164								164
Issuance of common stock upon exercise of options (in shares)				92,271
Vesting of RSUs (in shares)				145,204
Net loss													(18,606)				(18,606)
Balance at Dec. 31, 2019				$ 7				$ 213	306,108			$ (213)	(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									2,818								2,818
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									610								610
Issuance of common stock upon exercise of options (in shares)				503,448
Warrants issued in connection with long-term debt									3,570								3,570
Unrealized net gain on marketable securities										$ 3				3			3
Net loss													(51,853)				(51,853)
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									3,338								3,338
Issuance of common stock	$ 3				$ 21,078		$ 9,266							$ 21,081		$ 9,266
Issuance of common stock (in shares)	26,666,648		6,915,151
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																	(3)
Vesting of RSUs (in shares)				124,081
Warrants issued in connection with long-term debt									1,080								1,080
Unrealized net gain on marketable securities											$ (3)						(3)
Net loss				$ 0					0				(74,894)				(74,894)
Balance at Dec. 31, 2021				$ 12					$ 396,376				$ (387,117)				$ 9,271
Balance (in shares) at Dec. 31, 2021				121,396,033