Number of closed units.

No definition available.

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- Definition

Number of merged units.

+ References

No definition available.

+ Details

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- Definition

Number of units sold.

+ References

No definition available.

+ Details

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Namespace Prefix:	gff_
Data Type:	xbrli:integerItemType
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- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of revenue attributable to disposal group, including, but not limited to, discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721673-107760

+ Details

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Balance Type:	credit
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- Definition

Carrying amount as of the balance sheet date of the liability for remediation, site restoration, postclosure, monitoring commitments, or other exit costs associated with the sale, disposal or abandonment of a particular property resulting from unanticipated contamination of the assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.Y.Q4)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

+ Details

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Balance Type:	credit
Period Type:	instant

- 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

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- Details

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DISCONTINUED OPERATIONS (Details)	3 Months Ended		6 Months Ended		12 Months Ended
DISCONTINUED OPERATIONS (Details)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2008 unit	Sep. 30, 2017 USD ($)	Sep. 05, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of units sold \| unit					11
Number of closed units \| unit					1
Number of merged units \| unit					2
Environmental exit costs, costs accrued to date						$ 5,700,000
Revenue	$ 0	$ 0	$ 0	$ 0
PPC [Member] \| Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, including discontinued operation, consideration							$ 475,000,000
Revenue	$ 45,832,000	$ 111,958,000	$ 166,262,000	$ 226,780,000