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COMMITMENTS AND CONTINGENCIES (Details)	3 Months Ended		9 Months Ended		12 Months Ended
COMMITMENTS AND CONTINGENCIES (Details)	Jul. 31, 2020 USD ($) item	Jul. 31, 2019 USD ($)	Jul. 31, 2020 USD ($) item bu	Jul. 31, 2019 USD ($)	Oct. 31, 2019 USD ($) bu
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC
Commitments and contingencies
Rail Car Rehabilitation Liability			$ 825,000		$ 825,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn Contracts
Commitments and contingencies
Quantity of commitment \| bu			5,995,000		7,495,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn Contracts \| Short/Sale position
Commitments and contingencies
Quantity of commitment \| bu			2,015,000		4,150,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn Contracts \| Long/Purchase position
Commitments and contingencies
Quantity of commitment \| bu			2,215,000		3,345,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn Contracts \| Board Members
Commitments and contingencies
Amount of corn purchased	$ 1,482,000	$ 2,366,000	$ 2,323,000	$ 4,319,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Ethanol Contracts
Commitments and contingencies
Value of commitment	10,800,000		$ 10,800,000
Anticipated sales (as a percent)			97.00%
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Distillers' Grains \| Short/Sale position
Commitments and contingencies
Value of commitment	1,608,000		$ 1,608,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn oil \| Short/Sale position
Commitments and contingencies
Value of commitment	$ 504,000		$ 504,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Hopper rail cars
Commitments and contingencies
Equipment Lease, Quantity \| item	75		75
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn Forward Cash and Basis Contracts Purchase Commitments
Commitments and contingencies
Quantity of commitment \| bu			3,085,000
Asset impairment charges			$ 207,000		$ 0
Heron Lake BioEnergy, LLC
Commitments and contingencies
Rail Car Rehabilitation Costs			585,000		$ 551,000
Heron Lake BioEnergy, LLC \| Cost of Goods Sold
Commitments and contingencies
Rehabilitation Cost	$ 16,000		$ 70,000
Heron Lake BioEnergy, LLC \| Corn Contracts
Commitments and contingencies
Quantity of commitment \| bu			3,355,000		5,398,000
Heron Lake BioEnergy, LLC \| Corn Contracts \| Short/Sale position
Commitments and contingencies
Quantity of commitment \| bu			1,085,000		3,267,000
Heron Lake BioEnergy, LLC \| Corn Contracts \| Long/Purchase position
Commitments and contingencies
Quantity of commitment \| bu			2,055,000		2,131,000
Heron Lake BioEnergy, LLC \| Corn Contracts \| Board Members
Commitments and contingencies
Amount of corn purchased	57,000	$ 2,633,000	$ 5,872,000	$ 7,219,000
Heron Lake BioEnergy, LLC \| Ethanol Contracts
Commitments and contingencies
Value of commitment	6,069,000		$ 6,069,000
Anticipated sales (as a percent)			48.00%
Heron Lake BioEnergy, LLC \| Ethanol Contracts \| Long/Purchase position
Commitments and contingencies
Asset impairment charges			$ 824,000		$ 0
Heron Lake BioEnergy, LLC \| Distillers' Grains \| Short/Sale position
Commitments and contingencies
Value of commitment	325,000		325,000
Heron Lake BioEnergy, LLC \| Corn oil \| Short/Sale position
Commitments and contingencies
Value of commitment	$ 701,000		$ 701,000
Heron Lake BioEnergy, LLC \| Hopper rail cars
Commitments and contingencies
Equipment Lease, Quantity \| item	50		50
Heron Lake BioEnergy, LLC \| Corn Forward Cash and Basis Contracts Purchase Commitments
Commitments and contingencies
Quantity of commitment \| bu			4,613,000