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Inventories (Narrative) (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Inventories [Abstract]
Lower of cost or market adjustment	$ 0	$ 6,600,000

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- Definition

Lower Of Cost Or Market Adjustment.

+ References

No definition available.

+ Details

Name:	gpre_LowerOfCostOrMarketAdjustment
Namespace Prefix:	gpre_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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- References

No definition available.

+ Details

Name:	us-gaap_InventoryDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration