STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital	Accumulated Deficit
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	7,486		7,486
Exercise of employee stock options	1,036		1,036
Exercise of employee stock options (in shares)		363,109
Restricted stock awards	1	$ 1
Restricted stock awards (in shares)		726,224
Cancelled restricted common stock (in shares)		(122,091)
Net loss	(44,224)			(44,224)
Balance at Jun. 30, 2021	88,281	$ 216	896,390	(808,325)
Balance (in shares) at Jun. 30, 2021		215,559,148
Balance at Mar. 31, 2021	105,641	$ 215	891,081	(785,655)
Balance (in shares) at Mar. 31, 2021		215,257,674
Stock-based compensation	5,290		5,290
Exercise of employee stock options	20		20
Exercise of employee stock options (in shares)		10,667
Restricted stock awards		$ 1	(1)
Restricted stock awards (in shares)		412,898
Cancelled restricted common stock (in shares)		(122,091)
Net loss	(22,670)			(22,670)
Balance at Jun. 30, 2021	88,281	$ 216	896,390	(808,325)
Balance (in shares) at Jun. 30, 2021		215,559,148
Balance at Dec. 31, 2021	58,057	$ 216	900,693	(842,852)
Balance (in shares) at Dec. 31, 2021		216,127,443
Stock-based compensation	1,843		1,843
Restricted stock awards (in shares)		280,000
Cancelled restricted common stock (in shares)		(232,901)
Net loss	(19,720)			(19,720)
Balance at Jun. 30, 2022	40,180	$ 216	902,536	(862,572)
Balance (in shares) at Jun. 30, 2022		216,174,542
Balance at Mar. 31, 2022	49,122	$ 216	901,546	(852,640)
Balance (in shares) at Mar. 31, 2022		215,950,561
Stock-based compensation	990		990
Restricted stock awards (in shares)		280,000
Cancelled restricted common stock (in shares)		(56,019)
Net loss	(9,932)			(9,932)
Balance at Jun. 30, 2022	$ 40,180	$ 216	$ 902,536	$ (862,572)
Balance (in shares) at Jun. 30, 2022		216,174,542