Stock-Based Compensation - Service Based and Performance Based Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Weighted Average Grant-Date Fair Value
Stock based compensation expenses	$ 433	$ (1,461)	$ 197	$ (526)
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)	(104,168)
Forfeited (in shares)			(11,466)	(128,460)
Unvested at end of period (in shares)	342,604	420,062	342,604	420,062
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	4.66
Forfeited (in dollars per share)			4.81	4.30
Unvested at end of period (in dollars per share)	$ 1.17	$ 3.27	$ 1.17	$ 3.27
Stock based compensation expenses	$ 78	$ (4)	$ 182	$ 234
Unrecognized stock-based compensation expense	300		$ 300
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)				(905,625)
Unvested at end of period (in shares)		83,333		83,333
Weighted Average Grant-Date Fair Value
Unvested at beginning of period (in dollars per share)				$ 4.48
Forfeited (in dollars per share)				4.61
Unvested at end of period (in dollars per share)		$ 3.09		$ 3.09
Stock based compensation expenses	$ 0	$ (1,197)	$ 0	$ (1,025)
Outstanding performance-based restricted stock units (in shares)	0		0