Stock-Based Compensation - Service Based and Performance Based Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Weighted Average Grant-Date Fair Value
Stock based compensation expenses	$ (236)	$ 935
Restricted stock units - service based awards
Number of Shares
Unvested at beginning of period (in shares)	265,494	463,786
Granted (in shares)	10,050	16,304
Vested (in shares)	(26,354)	0
Forfeited (in shares)	(11,466)	(7,460)
Unvested at end of period (in shares)	237,724	472,630
Weighted Average Grant-Date Fair Value
Unvested at beginning of period (in dollars per share)	$ 2.60	$ 4.26
Granted (in dollars per share)	2.09	2.61
Vested (in dollars per share)	2.50	0
Forfeited (in dollars per share)	4.81	4.15
Unvested at end of period (in dollars per share)	$ 2.49	$ 4.21
Stock based compensation expenses	$ 104	$ 238
Unrecognized stock-based compensation expense	$ 100
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
Unvested at end of period (in shares)		988,958
Weighted Average Grant-Date Fair Value
Unvested at beginning of period (in dollars per share)		$ 4.48
Unvested at end of period (in dollars per share)		$ 4.48
Stock based compensation expenses	$ 0	$ 171
Outstanding performance-based restricted stock units (in shares)	0