Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Property, Plant and Equipment
Total property, plant and equipment, net	$ 67,602		$ 67,602		$ 56,233
Depreciation expense	26	$ 26	78	$ 73
Non project assets
Property, Plant and Equipment
Property, plant and equipment, gross	557		557		538
Less: accumulated depreciation	(343)		(343)		(265)
Total property, plant and equipment, net	214		214		273
Computers
Property, Plant and Equipment
Property, plant and equipment, gross	60		60		42
Furniture, fixtures, and equipment
Property, Plant and Equipment
Property, plant and equipment, gross	233		233		232
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	264		264		264
Project assets
Property, Plant and Equipment
Project assets in progress	67,388		67,388		55,960
Rio Grande
Property, Plant and Equipment
Project assets in progress	57,922		57,922		48,087
Rio Bravo
Property, Plant and Equipment
Project assets in progress	$ 9,466		$ 9,466		$ 7,873