Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Deficit - USD ($) shares in Thousands, $ in Thousands	Total	Series D Redeemable Convertible Preferred Stock [Member]	Non-redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2019	$ (2,888)		$ 5	$ 8	$ 103,490	$ (106,391)
Beginning balance at Dec. 31, 2019		$ 4,300
Beginning balance, shares at Dec. 31, 2019			5,255	7,539
Stock-based compensation	1,279				1,279
Net loss	(2,724)					(2,724)
Ending balance at Dec. 31, 2020	(4,333)		$ 5	$ 8	104,769	(109,115)
Ending balance at Dec. 31, 2020		4,300
Ending balance, shares at Dec. 31, 2020			5,255	7,539
Conversion of series I-1 preferred stock, shares			(1)	465
Stock-based compensation	644				644
Net loss	(899)					(899)
Ending balance at Dec. 31, 2021	$ (4,588)		$ 5	$ 8	$ 105,413	$ (110,014)
Ending balance at Dec. 31, 2021		$ 4,300
Ending balance, shares at Dec. 31, 2021			5,254	8,004