Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued liabilities
Compensation and benefits	$ 2,038	$ 2,641
Professional fees	186	131
LNG fuel and transportation	483	1,582
Accrued interest	79	134
Contract liabilities	418	185
Other taxes payable	300	163
Other operating expenses	292	182
Total accrued liabilities	$ 3,796	$ 5,018