CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (unaudited) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Convertible Preferred Stock Beginning balance, Shares at Dec. 31, 2020		17,031,887
Convertible Preferred Stock Beginning balance at Dec. 31, 2020		$ 281,342
Beginning balance, Shares at Dec. 31, 2020			1,200,335
Beginning balance at Dec. 31, 2020	$ (253,891)		$ 2	$ (51)	$ 9,703	$ (263,545)
Exercise of stock options	33				33
Exercise of stock options, Shares			12,797
Stock-based compensation	494				494
Net loss	(10,906)					(10,906)
Convertible Preferred Stock Ending balance, Shares at Mar. 31, 2021		17,031,887
Convertible Preferred Stock Ending balance at Mar. 31, 2021		$ 281,342
Ending balance, Shares at Mar. 31, 2021			1,213,132
Ending balance at Mar. 31, 2021	(264,270)		$ 2	(51)	10,230	(274,451)
Beginning balance, Shares at Dec. 31, 2021			26,336,536
Beginning balance at Dec. 31, 2021	72,063		$ 26	(51)	384,132	(312,044)
Employee stock plans	$ 242				242
Employee stock plans, Shares			82,572
Exercise of stock options, Shares	61,438
Stock-based compensation	$ 1,394				1,394
Net loss	(15,522)					(15,522)
Ending balance, Shares at Mar. 31, 2022			26,419,108
Ending balance at Mar. 31, 2022	$ 58,177		$ 26	$ (51)	$ 385,768	$ (327,566)