Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Beginning balance, value at Dec. 31, 2019	$ 27	$ 474,174	$ 72	$ (435,357)	$ 38,916
Beginning balance, shares at Dec. 31, 2019	27,374,653
Issuance of common stock, net of issuance costs	$ 11	12,589			12,600
Issuance of common stock, net of issuance costs, shares	10,854,710
Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs	$ 5	2,261			2,266
Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs, shares	5,450,000
Issuance of common stock upon exercise of warrants	$ 10	9,263			9,273
Issuance of common stock upon exercise of warrants, shares	10,073,298
Stock option exercises		31			31
Stock option exercises, shares	10,208
Stock-based compensation expense		7,258			7,258
Purchase of ESPP shares		75			75
Purchase of ESPP shares, shares	97,445
Vesting of restricted stock units	$ 2	(2)
Vesting of restricted stock units, shares	1,161,658
Shares withheld for tax withholding		(155)			(155)
Shares withheld for tax withholding, shares	(117,987)
Forfeiture of restricted stock awards
Forfeiture of restricted stock awards, shares	(46,886)
Other comprehensive income			(72)		(72)
Net loss				(42,854)	(42,854)
Ending balance, value at Dec. 31, 2020	$ 55	505,494		(478,211)	27,338
Ending balance, shares at Dec. 31, 2020	54,857,099
Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs	$ 7	1,248			1,255
Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs, shares	6,670,000
Issuance of common stock upon exercise of warrants	$ 10	6,661			6,671
Issuance of common stock upon exercise of warrants, shares	10,713,543
Stock option exercises		3			3
Stock option exercises, shares	2,500
Stock-based compensation expense		5,600			5,600
Purchase of ESPP shares		55			55
Purchase of ESPP shares, shares	101,900
Vesting of restricted stock units	$ 2	(2)
Vesting of restricted stock units, shares	3,126,564
Shares withheld for tax withholding		(463)			(463)
Shares withheld for tax withholding, shares	(608,144)
Forfeiture of restricted stock awards
Forfeiture of restricted stock awards, shares	(37,953)
Net loss				(30,187)	(30,187)
Reclassification of warrant liability upon exercise		8,964			8,964
Issuance of common stock upon exercise of pre-funded warrants	$ 8				8
Issuance of common stock upon exercise of pre-funded warrants, shares	7,658,953
Ending balance, value at Dec. 31, 2021	$ 82	$ 527,560		$ (508,398)	$ 19,244
Ending balance, shares at Dec. 31, 2021	82,484,462