Condensed Consolidated Statements of Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2020	$ 8,726	$ 148	$ 431,544	$ (422,975)	$ 9
Balance (in shares) at Dec. 31, 2020		148,078,974
Stock-based compensation expense	1,308		1,308
Issuance of common stock from vesting of restricted stock and exercise of stock options	53		53
Issuance of common stock from vesting of restricted stock and exercise of stock options (in shares)		412,699
Unrealized gain (loss) on marketable securities	7				7
Net loss	(10,660)			(10,660)
Balance at Mar. 31, 2021	(566)	$ 148	432,905	(433,635)	16
Balance (in shares) at Mar. 31, 2021		148,491,673
Balance at Dec. 31, 2021	$ (12,903)	$ 166	459,151	(472,216)	(4)
Balance (in shares) at Dec. 31, 2021	166,400,892	166,400,892
Stock-based compensation expense	$ 2,552		2,552
Issuance of common stock from vesting of restricted stock and exercise of stock options		$ 2	(2)
Issuance of common stock from vesting of restricted stock and exercise of stock options (in shares)		2,002,048
Surrender of shares due to tax withholding	(230)	$ (1)	(229)
Surrender of shares due to tax withholding (in shares)		(539,360)
Issuance of common stock from secondary offering, net	1,432	$ 4	1,428
Issuance of common stock from secondary offering, net (in shares)		3,549,360
Unrealized gain (loss) on marketable securities	(7)				(7)
Net loss	(16,495)			(16,495)
Balance at Mar. 31, 2022	$ (25,651)	$ 171	$ 462,900	$ (488,711)	$ (11)
Balance (in shares) at Mar. 31, 2022	171,412,940	171,412,940