Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance at Dec. 31, 2020	$ 194,271	$ 3		$ 579,755	$ (385,487)
Beginning balance, shares at Dec. 31, 2020		28,516,010
Issuance of common stock from exercise of stock options	412			412
Issuance of common stock from exercise of stock options, shares		36,998
401(k) matching contribution	323			323
401(k) matching contribution, shares		8,356
Vesting of restricted shares, shares		301,656
Stock-based compensation	3,818			3,818
ESPP shares issued	358			358
ESPP shares issued, shares		13,490
Net loss	(34,843)				(34,843)
Ending balance at Mar. 31, 2021	164,339	$ 3		584,666	(420,330)
Ending balance, shares at Mar. 31, 2021		28,876,510
Beginning balance at Dec. 31, 2021	$ 72,156	$ 3		601,523	(529,370)
Beginning balance, shares at Dec. 31, 2021	30,511,226	30,511,226	1
Cashless exercise of common stock warrants, shares		7,359,285	18
401(k) matching contribution	$ 254			254
401(k) matching contribution, shares		16,756
Vesting of restricted shares, shares		222,595
Stock-based compensation	5,775			5,775
ESPP shares issued	515			515
ESPP shares issued, shares		39,951
Net loss	(40,665)				(40,665)
Ending balance at Mar. 31, 2022	$ 38,035	$ 3		$ 608,067	$ (570,035)
Ending balance, shares at Mar. 31, 2022	38,149,813	38,149,813	19