Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	AOCI Attributable to Parent	Retained Earnings
Balances at Dec. 31, 2020	$ 139,832	$ 5	$ 415,824	$ 11	$ (276,008)
Balances (in shares) at Dec. 31, 2020		47,959
Issuance of common stock in connection with employee stock purchase plan	224		224
Issuance of common stock in connection with employee stock purchase plan (in shares)		38
Issuance of common stock in connection with exercise of stock options	146		146
Issuance of common stock in connection with exercise of stock options (in shares)		23
Issuance of common stock in connection with exercise of pre-funded warrants (in shares)		1,000
Stock-based compensation expense	1,757		1,757
Foreign currency translation adjustment	4			4
Unrealized gain (loss) on marketable securities	10			10
Net loss	(18,218)				(18,218)
Balances at Mar. 31, 2021	123,755	$ 5	417,951	25	(294,226)
Balances (in shares) at Mar. 31, 2021		49,020
Balances at Dec. 31, 2021	83,941	$ 5	425,765	(20)	(341,809)
Balances (in shares) at Dec. 31, 2021		49,355
Issuance of common stock in connection with employee stock purchase plan	184		184
Issuance of common stock in connection with employee stock purchase plan (in shares)		65
Stock-based compensation expense	2,101		2,101
Foreign currency translation adjustment	(13)			(13)
Unrealized gain (loss) on marketable securities	(120)			(120)
Net loss	(24,436)				(24,436)
Balances at Mar. 31, 2022	$ 61,657	$ 5	$ 428,050	$ (153)	$ (366,245)
Balances (in shares) at Mar. 31, 2022		49,420