Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Property, Plant and Equipment
Total property, plant and equipment, net	$ 96,026		$ 92,070
Depreciation expense	41	$ 29
Non project assets
Property, Plant and Equipment
Property, plant and equipment, gross	988		900
Less: accumulated depreciation	(583)		(542)
Total property, plant and equipment, net	405		358
Computers
Property, Plant and Equipment
Property, plant and equipment, gross	225		164
Furniture, fixtures, and equipment
Property, Plant and Equipment
Property, plant and equipment, gross	343		316
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	420		420
Project assets
Property, Plant and Equipment
Project assets in progress	95,621		91,712
Rio Grande
Property, Plant and Equipment
Project assets in progress	84,001		80,407
Rio Bravo
Property, Plant and Equipment
Project assets in progress	$ 11,620		$ 11,305