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COMMITMENTS AND CONTINGENCIES (Details)	3 Months Ended		6 Months Ended		12 Months Ended
COMMITMENTS AND CONTINGENCIES (Details)	Apr. 30, 2020 USD ($) item	Apr. 30, 2019 USD ($)	Apr. 30, 2020 USD ($) contract item bu	Apr. 30, 2019 USD ($)	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			2,640,000		7,495,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn Contracts \| Short/Sale position
Commitments and contingencies
Quantity of commitment \| bu			1,185,000		4,150,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn Contracts \| Long/Purchase position
Commitments and contingencies
Quantity of commitment \| bu			150,000		3,345,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn Contracts \| Board Members
Commitments and contingencies
Amount of corn purchased	$ 526,000	$ 605,000	$ 840,000	$ 1,954,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Ethanol Contracts \| Short/Sale position
Commitments and contingencies
Value of commitment	4,626,000		$ 4,626,000
Anticipated sales (as a percent)			48.00%
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Distillers' Grains \| Short/Sale position
Commitments and contingencies
Value of commitment	1,467,000		$ 1,467,000
Granite Falls Energy, LLC Excluding Heron Lake BioEnergy, LLC \| Corn oil \| Short/Sale position
Commitments and contingencies
Value of commitment	$ 111,000		$ 111,000
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			3,338,000
Asset impairment charges			$ 179,000		$ 0
Heron Lake BioEnergy, LLC
Commitments and contingencies
Rail Car Rehabilitation Costs			574,000
Heron Lake BioEnergy, LLC \| Cost of Goods Sold
Commitments and contingencies
Rehabilitation Cost	$ 12,000		$ 23,000
Heron Lake BioEnergy, LLC \| Corn Contracts
Commitments and contingencies
Quantity of commitment \| bu			1,246,000		5,398,000
Heron Lake BioEnergy, LLC \| Corn Contracts \| Short/Sale position
Commitments and contingencies
Quantity of commitment \| bu			246,000		3,267,000
Heron Lake BioEnergy, LLC \| Corn Contracts \| Long/Purchase position
Commitments and contingencies
Quantity of commitment \| bu			50,000		2,131,000
Heron Lake BioEnergy, LLC \| Corn Contracts \| Board Members
Commitments and contingencies
Amount of corn purchased	750,000	$ 2,636,000	$ 5,815,000	$ 4,585,000
Heron Lake BioEnergy, LLC \| Ethanol Contracts
Commitments and contingencies
Number of fixed or basis contracts to sell \| contract			0
Heron Lake BioEnergy, LLC \| Ethanol Contracts \| Long/Purchase position
Commitments and contingencies
Asset impairment charges			$ 83,000		$ 0
Heron Lake BioEnergy, LLC \| Distillers' Grains \| Short/Sale position
Commitments and contingencies
Value of commitment	557,000		557,000
Heron Lake BioEnergy, LLC \| Corn oil \| Short/Sale position
Commitments and contingencies
Value of commitment	$ 131,000		$ 131,000
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			5,613,000