Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance - December 31, 2019 at Dec. 31, 2018		$ 21	$ 414,840	$ 36	$ (342,864)	$ 72,033
Balance, shares at Dec. 31, 2018		21,447,088
Issuance of common stock, net of issuance costs of $1,319		$ 3	28,070			28,073
Issuance of common stock, net of issuance costs of $1,147, shares		3,473,008
Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs of $251
Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs of $251, shares
Issuance of common stock upon exercise of warrants
Issuance of common stock upon exercise of warrants, shares
Issuance of restricted stock awards		$ 2	(2)
Issuance of restricted stock awards, shares		1,579,919
Stock option exercise			529			529
Stock option exercises, shares		292,417
Stock-based compensation expense			31,440			31,440
Purchase of ESPP shares			99			99
Purchase of ESPP shares, shares		36,177
Vesting of restricted stock units		$ 1	(1)
Vesting of restricted stock units, shares		645,473
Shares withheld for tax withholding on vesting of restricted stock			(801)			(801)
Shares withheld for tax withholding on vesting of restricted stock, shares		(99,429)
Forfeiture of restricted stock awards
Forfeiture of restricted stock awards, shares
Other comprehensive loss				36		36
Net loss					(92,493)	(92,493)
Balance - December 31, 2020 at Dec. 31, 2019		$ 27	474,174	72	(435,357)	38,916
Balance, shares at Dec. 31, 2019		27,374,653
Issuance of common stock, net of issuance costs of $1,319		$ 11	12,589			12,600
Issuance of common stock, net of issuance costs of $1,147, shares		10,854,710
Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs of $251		$ 5	2,261			2,266
Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs of $251, 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 exercise			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 on vesting of restricted stock			(155)			(155)
Shares withheld for tax withholding on vesting of restricted stock, shares		(117,987)
Forfeiture of restricted stock awards
Forfeiture of restricted stock awards, shares		(46,886)
Other comprehensive loss				(72)		(72)
Net loss					(42,854)	(42,854)
Balance - December 31, 2020 at Dec. 31, 2020		$ 55	$ 505,494		$ (478,211)	$ 27,338
Balance, shares at Dec. 31, 2020		54,857,099