STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital	Accumulated Deficit
Balance at Dec. 31, 2019	$ 95,010	$ 182	$ 778,953	$ (684,125)
Balance (in shares) at Dec. 31, 2019		181,803,320
Stock-based compensation	6,829		6,829
Exercise of employee stock options	$ 442		442
Exercise of employee stock options (in shares)	338,333	252,799
Common stock issuance		2,814,673
Restricted stock awards		$ 1	(1)
Restricted stock awards (in shares)		805,900
Cancelled restricted common stock (in shares)		(194,897)
Issuance of common stock in connection with an at the market offering, net	$ 13,016	$ 3	13,013
Issuance of common stock in connection with an at the market offering, net of commissions and expenses of $400 (Shares)		2,814,673
Stock Issued During Period Shares Issuance Of Common Stock In Connection With Public Offering		29,110,111
Issuance of common stock in connection with a public offering, net of commissions and expenses of $5,900	88,661	$ 29	88,632
Issuance of common stock in connection with a public offering, net of commissions and expenses of $5,900 (in shares)		29,110,111
Net loss	(79,976)			(79,976)
Balance at Dec. 31, 2020	123,982	$ 215	887,868	(764,101)
Balance (in shares) at Dec. 31, 2020		214,591,906
Stock-based compensation	10,774		10,774
Exercise of employee stock options	$ 1,036		1,036
Exercise of employee stock options (in shares)	363,109	363,109
Common stock issuance		5,991
Restricted stock awards		$ 1	(1)
Restricted stock awards (in shares)		1,601,224
Cancelled restricted common stock (in shares)		(434,787)
Issuance of warrants	$ 1,016		1,016
Issuance of common stock in connection with an at the market offering, net of commissions and expenses of $400 (Shares)		5,991
Net loss	(78,751)			(78,751)
Balance at Dec. 31, 2021	$ 58,057	$ 216	$ 900,693	$ (842,852)
Balance (in shares) at Dec. 31, 2021		216,127,443