Acquisitions - (Details Textual) $ in Thousands, gal in Millions			12 Months Ended
	Mar. 15, 2016 USD ($) shares gal	Aug. 19, 2015 USD ($) shares gal	Dec. 31, 2017 USD ($) gal	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Production capacity per year | gal			520
Contingent consideration			$ 8,849	$ 28,931
Contingent consideration, current portion			25,545	17,637
Bargain purchase gain			$ 0	$ 0	$ 5,358
Sanimax
Business Acquisition [Line Items]
Production capacity per year | gal	20		20
Shares of Common Stock issued (in shares) | shares	500,000
Contingent consideration	$ 5,000		$ 2,603
Earnout payment period	7 years
Maximum Earnout Payments per year	$ 1,700
Contingent consideration, current portion			$ 1,160
Imperium Renewables, Inc.
Business Acquisition [Line Items]
Production capacity per year | gal		100
Shares of Common Stock issued (in shares) | shares		1,675,000
Earnout payment period		2 years
Bargain purchase gain		$ 5,358