Net Loss Per Share - Computation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss	$ (662)	$ (2,246)	$ (3,433)	$ (2,085)	$ (3,385)	$ (3,129)	$ (6,341)	$ (8,598)
Less: preferred stock dividends	0			(4)			(1)	(12)
Less: undeclared dividends	0			0			(366)	0
Induced conversion of Series A-2 Preferred Stock	0			0			(300)	0
Net loss attributable to common stockholders	(662)			(2,089)			(7,008)	(8,610)
Net loss attributable to common stockholders	$ (662)			$ (2,089)			$ (7,008)	$ (8,610)
Denominator:
Weighted-average number of shares of common stock for basic net loss per share (in shares)	30,739,000			5,257,000			25,121,000	5,237,000
Weighted-average number of shares of common stock for diluted net loss per share (in shares)	30,739,000			5,257,000			25,121,000	5,237,000
Basic net loss per share (in dollars per share)	$ (0.02)			$ (0.40)			$ (0.28)	$ (1.64)
Diluted net loss per share (in dollars per share)	$ (0.02)			$ (0.40)			$ (0.28)	$ (1.64)