Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2018	$ (48,045)	$ 41	$ 341,284		$ (389,370)
Beginning balance, shares at Dec. 31, 2018		40,936,735
Issuance of common stock from public offering, net of commissions, underwriting discounts and offering costs, value	60,527	$ 29	60,498
Issuance of common stock from public offering, net of commissions, underwriting discounts and offering costs, shares		28,818,578
Issuance of common stock from at the market equity offering, value	512		512
Issuance of common stock from at the market equity offering, shares		128,400
Issuance of common stock upon exercise of stock options, value	145		145
Issuance of common stock upon exercise of stock options, shares		90,125
Issuance of common stock upon vesting of RSUs, net of tax withholdings, value	176		176
Issuance of common stock upon vesting of RSUs, net of tax withholdings, shares		94,400
Issuance of common stock under ESPP plan, value	296		296
Issuance of common stock under ESPP plan, shares		75,014
Stock-based compensation expense	8,344		8,344
Net loss	(70,279)				(70,279)
Ending balance at Dec. 31, 2019	(48,324)	$ 70	411,255		(459,649)
Ending balance, shares at Dec. 31, 2019		70,143,252
Issuance of common stock from public offering, net of commissions, underwriting discounts and offering costs, value	243,748	$ 12	243,736
Issuance of common stock from public offering, net of commissions, underwriting discounts and offering costs, shares		12,075,000
Issuance of common stock from Securities Purchase Agreement, net of offering costs - related party, value	19,900	$ 1	19,899
Issuance of common stock from Securities Purchase Agreement, net of offering costs - related party, shares		959,002
Issuance of common stock from at the market equity offering, value	24,773	$ 6	24,767
Issuance of common stock from at the market equity offering, shares		5,787,681
Issuance of common stock upon exercise of stock options, value	14,421	$ 2	14,419
Issuance of common stock upon exercise of stock options, shares		2,214,011
Issuance of common stock upon vesting of RSUs, net of tax withholdings, value	120		120
Issuance of common stock upon vesting of RSUs, net of tax withholdings, shares		125,000
Issuance of common stock under ESPP plan, value	462		462
Issuance of common stock under ESPP plan, shares		155,293
Stock-based compensation expense	8,824		8,824
Other comprehensive loss	(47)			$ (47)
Net loss	(89,127)				(89,127)
Ending balance at Dec. 31, 2020	$ 174,750	$ 91	723,482	(47)	(548,776)
Ending balance, shares at Dec. 31, 2020	91,459,239	91,459,239
Issuance of common stock upon exercise of stock options, value	$ 1,299	$ 1	1,298
Issuance of common stock upon exercise of stock options, shares	329,112	329,112
Issuance of common stock upon vesting of RSUs, net of tax withholdings, shares		650
Issuance of common stock under ESPP plan, value	$ 827		827
Issuance of common stock under ESPP plan, shares		100,417
Stock-based compensation expense	20,222		20,222
Other comprehensive loss	(13)			(13)
Net loss	(65,578)				(65,578)
Ending balance at Dec. 31, 2021	$ 131,507	$ 92	$ 745,829	$ (60)	$ (614,354)
Ending balance, shares at Dec. 31, 2021	91,889,418	91,889,418