Stock-Based Compensation - Service Based Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Weighted Average Grant-Date Fair Value
Stock based compensation expenses	$ 475	$ 4,952
Restricted stock units - Service based awards
Number of Shares
Outstanding at beginning of period (in shares)	463,786	472,959
Granted (in shares)	208,993	244,063
Forfeited (in shares)	(159,724)	(28,916)
Vested (in shares)	(247,561)	(224,320)
Outstanding at end of period (in shares)	265,494	463,786
Weighted Average Grant-Date Fair Value
Outstanding at beginning of period (in dollars per share)	$ 4.26	$ 4.32
Granted (in dollars per share)	2.00	4.09
Forfeited (in dollars per share)	4.26	4.32
Vested (in dollars per share)	4.30	4.19
Outstanding at end of period (in dollars per share)	$ 2.60	$ 4.26
Stock based compensation expenses	$ 400	$ 1,600
Unrecognized stock-based compensation expenses	$ 200
Period of recognition for unrecognized stock-based compensation expenses	12 months
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

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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