XML 81 R71.htm IDEA: XBRL DOCUMENT v3.25.1

EMPLOYEE BENEFIT PLANS - Narrative (Details) - Pension Plan - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Mar. 31, 2025	Sep. 30, 2025
Defined Benefit Plan Disclosure [Line Items]
Lump sum distribution for plan termination	$ 4,830
Subsequent Event | Forecast
Defined Benefit Plan Disclosure [Line Items]
Plan assets, decrease for assets transferred from plan		$ 10,895

X

- Definition

Defined Benefit Plan, Lump Sum Distribution For Plan Termination

+ References

No definition available.

+ Details

Name:	gff_DefinedBenefitPlanLumpSumDistributionForPlanTermination
Namespace Prefix:	gff_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of increase (decrease) in plan assets of defined benefit plan from assets transferred into (from) plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanAssetsTransferredToFromPlan
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

X

- Details

Name:	us-gaap_RetirementPlanTypeAxis=gff_HunterFanPensionPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: