Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Other Comprehensive Gain/(Loss) [Member]	Accumulated Deficit [Member]	Noncontrolling Interest [Member]	Convertible Preferred Stock Preferred Stock
Beginning balance at Dec. 31, 2018	$ 33,650	$ 2	$ 332,407	$ (60)	$ (298,701)		$ 2
Beginning balance, Shares at Dec. 31, 2018		2,186,389					2,285,952
Conversion of preferred stock to common stock, shares		229,283					(641,991)
Issuance of common stock upon release of restricted stock units, Shares		7,487
Issuance of common stock pursuant to employee stock purchase plan	13		13
Issuance of common stock pursuant to employee stock purchase plan, Shares		3,117
Issuance of common stock from at-the-market offerings, net of offering costs	4,405	$ 1	4,404
Issuance of common stock from at the market offerings, net of offering costs, Shares		805,357
Issuance of common stock from registered direct offering, net of offering costs	4,918	$ 1	4,917
Issuance of common stock from registered direct offering, net of offering costs, Shares		660,154
Stock-based compensation	1,783		1,783
Net unrealized gain (loss) on investments, net of tax	20			20
Net loss	(23,763)				(23,603)	$ (160)
Ending balance at Dec. 31, 2019	21,026	$ 4	343,524	(40)	(322,304)	(160)	$ 2
Ending balance, Shares at Dec. 31, 2019		3,891,787					1,643,961
Conversion of preferred stock to common stock		$ 1	1				$ (2)
Conversion of preferred stock to common stock, shares		587,444					(1,643,961)
Issuance of common stock from underwritten follow-on offering, net of offering costs	18,779	$ 4	18,775
Issuance of common stock from underwritten follow-on offering, net of offering costs, Shares		4,870,588
Issuance of common stock upon release of restricted stock units, Shares		8,678
Issuance of common stock pursuant to employee stock purchase plan	10		10
Issuance of common stock pursuant to employee stock purchase plan, Shares		3,382
Issuance of common stock from at-the-market offerings, net of offering costs	6,437	$ 2	6,435
Issuance of common stock from at the market offerings, net of offering costs, Shares		1,657,075
Stock-based compensation	1,465		1,465
Net unrealized gain (loss) on investments, net of tax	(3)			(3)
Net loss	(16,230)				(16,224)	(6)
Ending balance at Dec. 31, 2020	31,484	$ 11	370,210	(43)	(338,528)	(166)
Ending balance, Shares at Dec. 31, 2020		11,018,954
Issuance of common stock from underwritten follow-on offering, net of offering costs	80,646	$ 11	80,635
Issuance of common stock from underwritten follow-on offering, net of offering costs, Shares		10,781,250
Issuance of common stock upon release of restricted stock units, Shares		4,177
Issuance of common stock upon exercise of stock options	$ 62		62
Issuance of common stock upon exercise of stock options, Shares	10,751	10,751
Issuance of common stock pursuant to employee stock purchase plan	$ 11		11
Issuance of common stock pursuant to employee stock purchase plan, Shares		3,382
Issuance of common stock from at-the-market offerings, net of offering costs	14,070	$ 3	14,067
Issuance of common stock from at the market offerings, net of offering costs, Shares		2,974,521
Issuance of common stock from committed purchase agreement, net of offering costs	15,236	$ 3	15,233
Issuance of common stock from committed purchase agreement, net of offering costs, Shares		3,000,000
Stock-based compensation	1,614		1,614
Net unrealized gain (loss) on investments, net of tax	(220)			(220)
Net loss	(33,777)				(33,768)	(9)
Ending balance at Dec. 31, 2021	$ 109,126	$ 28	$ 481,832	$ (263)	$ (372,296)	$ (175)
Ending balance, Shares at Dec. 31, 2021		27,793,035