COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	9 Months Ended
Jun. 30, 2021	Apr. 30, 2009
Commitments and Contingencies Disclosure [Abstract]
Site contingency, ownership period	3 years
Net capital cost value in proposed remedial action plan		$ 10,000

Amount of net capital cost value in Proposed Remedial Action Plan as of the reporting date.

No definition available.

Name:	gff_NetCapitalCostValueInProposedRemediaActionPlan
Namespace Prefix:	gff_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant