Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment
Total property, plant and equipment, net	$ 104,198		$ 104,198		$ 92,070
Depreciation expense	43	$ 48	85	$ 77
Non project assets
Property, Plant and Equipment
Property, plant and equipment, gross	1,096		1,096		900
Less: accumulated depreciation	(627)		(627)		(542)
Total property, plant and equipment, net	469		469		358
Computers
Property, Plant and Equipment
Property, plant and equipment, gross	317		317		164
Furniture, fixtures, and equipment
Property, Plant and Equipment
Property, plant and equipment, gross	359		359		316
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	420		420		420
Project assets
Property, Plant and Equipment
Project assets in progress	103,729		103,729		91,712
Rio Grande
Property, Plant and Equipment
Project assets in progress	91,949		91,949		80,407
Rio Bravo
Property, Plant and Equipment
Project assets in progress	$ 11,780		$ 11,780		$ 11,305