Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued liabilities
Compensation and benefits	$ 2,359	$ 2,641
Professional fees	234	131
LNG fuel and transportation	1,366	1,582
Accrued interest	59	134
Contract liabilities	221	185
Other taxes payable	192	163
Other operating expenses	59	182
Total accrued liabilities	$ 4,490	$ 5,018