Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balance at beginning of period at Dec. 31, 2019	$ 186,348	$ 7	$ 812,133	$ 80	$ (625,872)
Balance at beginning of period (in shares) at Dec. 31, 2019		68,882,459
Issuance of common stock upon exercise of stock options	92		92
Issuance of common stock upon exercise of stock options (Shares)		63,633
Stock-based compensation expense	7,324		7,324
Net loss	(50,986)				(50,986)
Net unrealized gain (loss) on marketable securities	(72)			(72)
Balance at end of period at Dec. 31, 2020	142,706	$ 7	819,549	8	(676,858)
Balance at end of period (in shares) at Dec. 31, 2020		68,946,092
Issuance of common stock upon exercise of stock options	$ 219		219
Issuance of common stock upon exercise of stock options (Shares)	106,847	106,847
Stock-based compensation expense	$ 9,996		9,996
Issuance of common stock and pre-funded warrants, net of issuance costs	70,035	$ 1	70,034
Issuance of common stock and pre-funded warrants, net of issuance costs Shares		15,625,000
Net loss	(89,998)				(89,998)
Net unrealized gain (loss) on marketable securities	(21)			(21)
Balance at end of period at Dec. 31, 2021	$ 132,937	$ 8	$ 899,798	$ (13)	$ (766,856)
Balance at end of period (in shares) at Dec. 31, 2021		84,677,939