Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Cost	$ 33,586	$ 33,586
Accumulated Amortization	(7,642)	(6,459)
Net	25,944	27,127
Raw material supply agreement
Finite-Lived Intangible Assets [Line Items]
Cost	6,230	6,230
Accumulated Amortization	(2,630)	(2,408)
Net	$ 3,600	$ 3,822
Weighted Average Remaining Life	7 years 6 months	8 years
Renewable diesel technology
Finite-Lived Intangible Assets [Line Items]
Cost	$ 8,300	$ 8,300
Accumulated Amortization	(2,259)	(1,983)
Net	$ 6,041	$ 6,317
Weighted Average Remaining Life	11 years	11 years 6 months
Ground lease
Finite-Lived Intangible Assets [Line Items]
Cost	$ 200	$ 200
Accumulated Amortization	(149)	(141)
Net	$ 51	$ 59
Weighted Average Remaining Life	3 years 4 months 24 days	3 years 10 months 24 days
Acquired customer relationships
Finite-Lived Intangible Assets [Line Items]
Cost	$ 2,900	$ 2,900
Accumulated Amortization	(831)	(686)
Net	$ 2,069	$ 2,214
Weighted Average Remaining Life	7 years 1 month	7 years 7 months
In-process research and development
Finite-Lived Intangible Assets [Line Items]
Cost	$ 15,956	$ 15,956
Accumulated Amortization	(1,773)	(1,241)
Net	$ 14,183	$ 14,715
Weighted Average Remaining Life	13 years 4 months	13 years 10 months