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Inventories (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Inventories [Abstract]
Lower of cost or market adjustment	$ 6.6	$ 6.0

X

- 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