Consolidated Statements of Changes in Stockholders’ (Deficit) Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive loss
Beginning balance (in shares) at Dec. 31, 2020		108,071,249
Beginning balance at Dec. 31, 2020	$ (18,006)	$ 11	$ 391,175	$ (404,629)	$ (4,563)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under Employee Stock Purchase Plan (in shares)		34,696
Issuance of common stock under Employee Stock Purchase Plan	72		72
Issuance of common stock upon exercise of options (in shares)		153,278
Issuance of common stock upon exercise of options	244		244
Issuance of vested restricted stock units (in shares)		10,937
Issuance of vested restricted stock units	0
Issuance of common stock through at-the-market offering, net (in shares)		4,706,844
Issuance of common stock through at-the-market offering, net	20,943		20,943
Stock-based compensation expense	1,780		1,780
Foreign currency translation adjustment	(6)				(6)
Unrealized (losses) on marketable securities	(1)				(1)
Net income (loss)	(24,597)			(24,597)
Ending balance (in shares) at Mar. 31, 2021		112,977,004
Ending balance at Mar. 31, 2021	$ (19,571)	$ 11	414,214	(429,226)	(4,570)
Beginning balance (in shares) at Dec. 31, 2021	123,622,965	123,622,965
Beginning balance at Dec. 31, 2021	$ 22,521	$ 12	457,391	(430,316)	(4,566)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under Employee Stock Purchase Plan (in shares)		81,057
Issuance of common stock under Employee Stock Purchase Plan	127		127
Issuance of common stock upon exercise of options (in shares)		11,262
Issuance of common stock upon exercise of options	21		21
Issuance of vested restricted stock units (in shares)		89,142
Issuance of vested restricted stock units	0
Issuance of common stock through at-the-market offering, net (in shares)		576,418
Issuance of common stock through at-the-market offering, net	1,675		1,675
Other financing fees	(79)		(79)
Stock-based compensation expense	2,753		2,753
Foreign currency translation adjustment	(32)				(32)
Unrealized (losses) on marketable securities	0
Net income (loss)	$ 28,778			28,778
Ending balance (in shares) at Mar. 31, 2022	124,380,844	124,380,844
Ending balance at Mar. 31, 2022	$ 55,764	$ 12	$ 461,888	$ (401,538)	$ (4,598)