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v3.21.2

REVENUE - Narrative (Details) - Construction and Professional Products and Home and Building Products Segments | 12 Months Ended
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Sep. 30, 2021
Minimum |
Revenue, Initial Application Period Cumulative Effect Transition [Line Items] |
Payment term | 15 days
Maximum |
Revenue, Initial Application Period Cumulative Effect Transition [Line Items] |
Payment term | 90 days

X
- Definition Revenue From Contract With Customer, Payment Term + References No definition available. + Details
Name: | gff_RevenueFromContractWithCustomerPaymentTerm
Namespace Prefix: | gff_
Data Type: | xbrli:durationItemType
Balance Type: | na
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_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=gff_ConstructionandProfessionalProductsandHomeandBuildingProductsSegmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |