Summary of Significant Accounting Policies (Details Textual)		3 Months Ended					9 Months Ended
	Jun. 02, 2016 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) renewable_identification_number	Sep. 30, 2019 USD ($)	Feb. 29, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2016 USD ($)
Business Acquisition [Line Items]
Restricted cash		$ 3,000,000			$ 3,000,000		$ 3,000,000	$ 3,000,000		$ 3,000,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments		13,992,000	$ 20,860,000	$ 17,829,000		$ 152,000
Gain (loss) on debt extinguishment		18,000			0		1,809,000	(2,000)
Goodwill		16,080,000			16,080,000		16,080,000	16,080,000		16,080,000
Tangible Asset Impairment Charges					11,145,000
Equipment
Business Acquisition [Line Items]
Tangible Asset Impairment Charges		18,984,000
Biodiesel property, plant and equipment
Business Acquisition [Line Items]
Tangible Asset Impairment Charges		272,000
June 2018 Program
Business Acquisition [Line Items]
Security repurchase program, amount authorized to be repurchased												$ 75,000,000
January 2019 Program
Business Acquisition [Line Items]
Security repurchase program, amount authorized to be repurchased											$ 75,000,000
February 2020 Program
Business Acquisition [Line Items]
Security repurchase program, amount authorized to be repurchased									$ 100,000,000
January 2019 Program and February 2020 Program
Business Acquisition [Line Items]
Security repurchase program, remaining amounts		91,914,000					91,914,000
2036 Senior Convertible Notes Repurchases | Convertible Notes
Business Acquisition [Line Items]
Face amount	$ 152,000,000												$ 152,000,000
Interest rate	4.00%												4.00%
Convertible Notes Repurchases	$ 147,118,000	18,086,000			$ 0		75,890,000	$ 0
Principal amount of debt repurchased		5,000,000					30,008,000
Gain (loss) on debt extinguishment		18,000					1,809,000
2036 Senior Convertible Notes Repurchases | Convertible Notes | January 2019 Program
Business Acquisition [Line Items]
Convertible Notes Repurchases		10,000,000					67,804,000
2036 Senior Convertible Notes Repurchases | Convertible Notes | February 2020 Program
Business Acquisition [Line Items]
Convertible Notes Repurchases		8,086,000					8,086,000
Services
Business Acquisition [Line Items]
Goodwill		16,080,000					$ 16,080,000			$ 16,080,000
Minimum
Business Acquisition [Line Items]
RINs per gallon | renewable_identification_number							1.5
Allowed RINs per gallon | renewable_identification_number							0
Maximum
Business Acquisition [Line Items]
RINs per gallon | renewable_identification_number							1.7
Allowed RINs per gallon | renewable_identification_number							2.5
Common Stock - Additional Paid-in Capital
Business Acquisition [Line Items]
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments		$ 13,992,000	$ 20,860,000	$ 17,829,000		$ 152,000	$ 52,681,000