Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment
Total property, plant and equipment, net	$ 73,226	$ 56,233
Depreciation expense	106	100	$ 80
Impairment loss on capital projects		506
Impairment charges related to the original Pelican Island site		360
Impairment charges related to other noncore projects		146
Non project assets
Property, Plant and Equipment
Property, plant and equipment, gross	579	538
Less: accumulated depreciation	(371)	(265)
Total property, plant and equipment, net	208	273
Computers
Property, Plant and Equipment
Property, plant and equipment, gross	69	42
Furniture, fixtures, and equipment
Property, Plant and Equipment
Property, plant and equipment, gross	246	232
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	264	264
Project assets
Property, Plant and Equipment
Project assets in progress	73,018	55,960
Rio Grande
Property, Plant and Equipment
Project assets in progress	62,866	48,087
Rio Bravo
Property, Plant and Equipment
Project assets in progress	$ 10,152	$ 7,873