Acquisition (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jul. 01, 2020
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net							$ 67,820
Business Acquisition, Transaction Costs	$ 3,900
Net revenue		$ 225,580	$ 157,405	$ 597,769	$ 483,853
Net Income (Loss) Attributable to Parent		1,411	8,852	17,515	(3,872)
Product sales
Business Acquisition [Line Items]
Net revenue		216,187	$ 155,188	569,691	$ 478,989
General and administrative expenses
Business Acquisition [Line Items]
Business Acquisition, Transaction Costs	3,600
Georgia Biomass
Business Acquisition [Line Items]
Total consideration	175,000
Cash payment	168,300
Identified Net Assets Acquired	(147,283)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	162,970
Revenue				680,883		$ 845,340
Net income				28,778		$ 10,497
Net revenue		26,500		26,500
Net Income (Loss) Attributable to Parent		$ 100		$ 100
Georgia Biomass | Cash
Business Acquisition [Line Items]
Identified Net Assets Acquired	(1,516)
Georgia Biomass | Accounts receivable
Business Acquisition [Line Items]
Identified Net Assets Acquired	(124)
Georgia Biomass | Inventories
Business Acquisition [Line Items]
Identified Net Assets Acquired	(5,774)
Georgia Biomass | Prepaid expenses and other current assets
Business Acquisition [Line Items]
Identified Net Assets Acquired	(872)
Georgia Biomass | Intangible assets
Business Acquisition [Line Items]
Identified Net Assets Acquired	(5,400)
Georgia Biomass | Property, plant and equipment
Business Acquisition [Line Items]
Identified Net Assets Acquired	(171,798)
Georgia Biomass | Operating lease right-of-use assets
Business Acquisition [Line Items]
Identified Net Assets Acquired	(14,716)
Georgia Biomass | Accounts payable
Business Acquisition [Line Items]
Identified Net Assets Acquired	(3,225)
Georgia Biomass | Accrued and other current liabilities
Business Acquisition [Line Items]
Identified Net Assets Acquired	(7,121)
Georgia Biomass | Current portion of long-term finance lease obligations
Business Acquisition [Line Items]
Identified Net Assets Acquired	(926)
Georgia Biomass | Long-term finance lease obligations
Business Acquisition [Line Items]
Identified Net Assets Acquired	(3,733)
Georgia Biomass | Long-term operating lease liabilities
Business Acquisition [Line Items]
Identified Net Assets Acquired	(13,356)
Georgia Biomass | Deferred tax liability, net
Business Acquisition [Line Items]
Identified Net Assets Acquired	(14,076)
Georgia Biomass | Intangible liabilities
Business Acquisition [Line Items]
Identified Net Assets Acquired	(9,600)
Georgia Biomass | Other long-term liabilities
Business Acquisition [Line Items]
Identified Net Assets Acquired	(880)
Georgia Biomass | Goodwill
Business Acquisition [Line Items]
Identified Net Assets Acquired	(15,687)
Purchase Price Reconciliation
Business Acquisition [Line Items]
Cash payment	168,338
Reimbursement to the Partnership of certain acquisition-related costs, net	161
Settlement of payable from the Partnership to Georgia Biomass	(3,684)
Payment in relation to the Georgia Biomass Acquisition	164,815
Receivable from purchase price adjustment	(1,845)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	$ 162,970