Stock-Based Compensation - Service Based and Performance Based Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Weighted Average Grant-Date Fair Value
Stock based compensation expenses	$ 361	$ 250	$ 558	$ (276)
Restricted stock units - service based awards
Number of Shares
Unvested at beginning of period (in shares)			265,494	463,786
Granted (in shares)			310,050	188,904
Vested (in shares)			(221,474)	(247,561)
Forfeited (in shares)			(11,799)	(159,724)
Unvested at end of period (in shares)	342,271	245,405	342,271	245,405
Weighted Average Grant-Date Fair Value
Unvested at beginning of period (in dollars per share)			$ 2.60	$ 4.26
Granted (in dollars per share)			0.90	2.09
Vested (in dollars per share)			2.38	4.30
Forfeited (in dollars per share)			4.81	4.26
Unvested at end of period (in dollars per share)	$ 1.17	$ 2.72	$ 1.17	$ 2.72
Stock based compensation expenses	$ 81	$ 9	$ 263	$ 243
Unrecognized stock-based compensation expense	200		$ 200
Unrecognized stock-based compensation expense, weighted average remaining term (in years) (less than)			1 year
Restricted stock units - service based awards | Minimum
Weighted Average Grant-Date Fair Value
Vesting period			1 year
Restricted stock units - service based awards | Maximum
Weighted Average Grant-Date Fair Value
Vesting period			3 years
Restricted stock units - performance based awards
Number of Shares
Unvested at beginning of period (in shares)				988,958
Forfeited (in shares)				(988,958)
Unvested at end of period (in shares)		0		0
Weighted Average Grant-Date Fair Value
Unvested at beginning of period (in dollars per share)				$ 4.48
Forfeited (in dollars per share)				4.48
Unvested at end of period (in dollars per share)		$ 0		$ 0
Stock based compensation expenses	$ 0	$ (123)	$ 0	$ (1,148)
Outstanding performance-based restricted stock units (in shares)	0		0