Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Total
Balance at Dec. 31, 2020	$ 25	$ 195,410	$ (1)	$ (172,540)	$ 22,894
Balance, shares at Dec. 31, 2020	25,550
Issuance of shares upon exercise of stock options		449			449
Issuance of shares upon exercise of stock options, shares	40
Issuance of shares under employee stock purchase plan		430			430
Issuance of shares under employee stock purchase plan, shares	68
Issuance of shares upon exercise of warrants	$ 1	3,333			3,334
Issuance of shares upon exercise of warrants, shares	585
Issuance of common stock in an at-the-market equity offering, net of issuance costs of $446		4,963			4,963
Issuance of common stock in an at-the-market equity offering, net of issuance costs of $446, shares	158
Stock-based compensation expense		6,965			6,965
Unrealized gain on available-for-sale securities			$ 1		1
Net loss				(18,639)	(18,639)
Balance at Mar. 31, 2021	$ 26	211,550		(191,179)	20,397
Balance, shares at Mar. 31, 2021	26,401
Balance at Dec. 31, 2021	$ 29	271,861		(236,200)	$ 35,690
Balance, shares at Dec. 31, 2021	29,716				29,716
Issuance of shares under employee stock purchase plan		372			$ 372
Issuance of shares under employee stock purchase plan, shares	86
Stock-based compensation expense		2,007			2,007
Net loss				(17,273)	(17,273)
Balance at Mar. 31, 2022	$ 29	$ 274,240		$ (253,473)	$ 20,796
Balance, shares at Mar. 31, 2022	29,802				29,802