Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment
Total property, plant and equipment, net	$ 88,870		$ 88,870		$ 73,226
Depreciation expense	50	$ 26	127	$ 78
Non project assets
Property, Plant and Equipment
Property, plant and equipment, gross	822		822		579
Less: accumulated depreciation	(498)		(498)		(371)
Total property, plant and equipment, net	324		324		208
Computers
Property, Plant and Equipment
Property, plant and equipment, gross	119		119		69
Furniture, fixtures, and equipment
Property, Plant and Equipment
Property, plant and equipment, gross	305		305		246
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	398		398		264
Project assets
Property, Plant and Equipment
Project assets in progress	88,546		88,546		73,018
Rio Grande
Property, Plant and Equipment
Project assets in progress	77,224		77,224		62,866
Rio Bravo
Property, Plant and Equipment
Project assets in progress	$ 11,322		$ 11,322		$ 10,152