Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		0	16,616,165
Beginning balance at Dec. 31, 2019	$ (23,909)	$ 0	$ 2	$ 307,403	$ (331,314)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock issued (in shares)		1,955,000
Preferred stock issued, net	45,104			45,104
Warrants exercised (in shares)			72,112
Warrants exercised	1,470			1,470
Stock option exercised (in shares)			684,441
Stock options exercised	5,742			5,742
401(k) employer match (in shares)			12,687
401(k) employer match	386			386
Stock-based compensation expense (in shares)			25,724
Stock-based compensation expense	5,799			5,799
Net loss	(19,481)				(19,481)
Ending balance (in shares) at Sep. 30, 2020		1,955,000	17,411,129
Ending balance at Sep. 30, 2020	15,111	$ 0	$ 2	365,904	(350,795)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		0	17,055,609
Beginning balance at Jun. 30, 2020	(30,044)	$ 0	$ 2	315,076	(345,122)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred stock issued (in shares)		1,955,000
Preferred stock issued, net	45,104			45,104
Warrants exercised (in shares)			61,063
Warrants exercised	1,450			1,450
Stock option exercised (in shares)			288,419
Stock options exercised	2,277			2,277
401(k) employer match (in shares)			6,038
401(k) employer match	246			246
Stock-based compensation expense	1,751			1,751
Net loss	(5,673)				(5,673)
Ending balance (in shares) at Sep. 30, 2020		1,955,000	17,411,129
Ending balance at Sep. 30, 2020	15,111	$ 0	$ 2	365,904	(350,795)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		1,955,000	17,411,129
Beginning balance (in shares)		3,770,265	17,543,218
Beginning balance at Dec. 31, 2020	60,751	$ 0	$ 2	414,773	(354,024)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred dividends declared	(6,712)			(6,712)
Warrants exercised (in shares)			1,184,641
Warrants exercised	58			58
Stock option exercised (in shares)			395,181
Stock options exercised	5,584			5,584
401(k) employer match (in shares)			32,441
401(k) employer match	840			840
Stock-based compensation expense	8,871			8,871
Net loss	(17,093)				(17,093)
Ending balance (in shares) at Sep. 30, 2021		3,770,265	19,155,481
Ending balance at Sep. 30, 2021	52,299	$ 0	$ 2	423,414	(371,117)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		3,770,265	18,657,840
Beginning balance at Jun. 30, 2021	59,033	$ 0	$ 2	422,265	(363,234)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred dividends declared	(2,274)			(2,274)
Warrants exercised (in shares)			463,567
Warrants exercised	0
Stock option exercised (in shares)			16,083
Stock options exercised	183			183
401(k) employer match (in shares)			17,991
401(k) employer match	330			330
Stock-based compensation expense	2,910			2,910
Net loss	(7,883)				(7,883)
Ending balance (in shares) at Sep. 30, 2021		3,770,265	19,155,481
Ending balance at Sep. 30, 2021	$ 52,299	$ 0	$ 2	$ 423,414	$ (371,117)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)		3,770,265	19,155,481