Debt Extinguishment, Redemption Interest

No definition available.

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Namespace Prefix:	gff_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Debt Extinguishment, Tender Offer Net Premium

+ References

No definition available.

+ Details

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Namespace Prefix:	gff_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Debt Instrument Issuance Price Percentage

+ References

No definition available.

+ Details

Name:	gff_DebtInstrumentIssuancePricePercentage
Namespace Prefix:	gff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Lessee, Finance Lease, Number Of Options to Extend

+ References

No definition available.

+ Details

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Namespace Prefix:	gff_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility, Maximum Borrowing Capacity Increase (Decrease)

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line of Credit Facility, Maximum Borrowing Capacity, Accordion Feature

+ References

No definition available.

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

- Definition

Long-term Line of Credit, Balance Increase (Decrease)

+ References

No definition available.

+ Details

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

- Definition

Maximum percentage of equity interest of subsidiaries borrowings guaranteed.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

+ References

No definition available.

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
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-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
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-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Balance Type:	na
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

Name:	us-gaap_DebtInstrumentLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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

- Definition

Amount of payment greater than the preceding installment payments to be paid at final maturity date of debt.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Term of lessee's finance lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918673-209980

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase (decrease) of the credit facility.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
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-Topic 210
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99376301&loc=d3e1314-112600

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

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-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

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

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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Balance Type:	debit
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Period Type:

LONG-TERM DEBT - Narrative (Details) $ in Thousands				1 Months Ended			3 Months Ended			9 Months Ended		12 Months Ended
LONG-TERM DEBT - Narrative (Details) $ in Thousands	Jun. 22, 2020 USD ($)	Feb. 19, 2020 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2019 AUD ($)	Jul. 31, 2018 GBP (£)	Nov. 30, 2012 CAD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2020 AUD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) option	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 GBP (£)	Jun. 30, 2020 USD ($)	Jun. 30, 2020 AUD ($)	Jun. 30, 2020 CAD ($)	Jun. 29, 2020 AUD ($)	Mar. 31, 2020 AUD ($)	Jan. 30, 2020 USD ($)	Jan. 29, 2020 USD ($)	Sep. 30, 2019 USD ($)
Debt Instrument [Line Items]
Debt outstanding														$ 1,149,903,000							$ 1,114,131,000
Loss from debt extinguishment							$ 1,235,000		$ 0	$ 7,925,000	$ 0
Basis spread on variable rate						1.30%
Mortgage loan balance														$ 1,132,600,000							1,104,274,000
Troy, Ohio
Debt Instrument [Line Items]
Percentage bearing fixed interest, percentage rate													5.00%	5.00%	5.00%	5.00%
Ocala, Florida
Debt Instrument [Line Items]
Percentage bearing fixed interest, percentage rate													2.90%	2.90%	2.90%	2.90%
Number of option to extend \| option										1
Lease renewal term													5 years	5 years	5 years	5 years
Revolver due 2025
Debt Instrument [Line Items]
Maximum borrowing capacity																			$ 400,000	$ 350,000,000
Maximum borrowing capacity, accordion feature																			100,000,000	50,000,000
Maximum percentage of equity interest of subsidiaries borrowings guaranteed										65.00%
Long-term line of credit														$ 104,181,000
Outstanding standby letters of credit														21,617,000
Remaining borrowing capacity														$ 274,202,000
Revolver due 2025 \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate										1.25%
Revolver due 2025 \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate										2.25%
Term Loan
Debt Instrument [Line Items]
Periodic payment terms, balloon payment to be paid \| £					£ 7,700,000
Interest rate at period end													2.33%	2.33%	2.33%	2.33%
Term Loan \| Northcote Holdings Pty. Ltd
Debt Instrument [Line Items]
Face amount				$ 29,625,000
Term Loan \| Ames UK
Debt Instrument [Line Items]
Face amount \| £					14,000,000
Debt instrument, periodic payment, principal \| £					£ 350,000
Term Loan \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate					2.25%
Mortgages \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate					1.80%
Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate					1.75%
Interest rate at period end													1.85%	1.85%	1.85%	1.85%
Revolving Credit Facility \| Ames UK
Debt Instrument [Line Items]
Face amount \| £					£ 5,000,000
Term and Mortgage Loans \| Ames UK
Debt Instrument [Line Items]
Mortgage loan balance													£ 15,398,000	$ 18,975,000
Letter of Credit Subfacility \| Revolver due 2025
Debt Instrument [Line Items]
Maximum borrowing capacity																			100,000,000	50,000,000
Multicurrency Subfacility \| Revolver due 2025
Debt Instrument [Line Items]
Maximum borrowing capacity																			$ 200,000,000	$ 100,000,000
Receivables Purchase Facility
Debt Instrument [Line Items]
Basis spread on variable rate				1.35%
Mortgage loan balance																	$ 15,000,000	$ 10,000,000
Debt instrument, interest rate, effective percentage													1.49%	1.49%	1.49%	1.49%
Increase in receivables purchase line								$ (5,000,000)
Senior notes due 2028
Debt Instrument [Line Items]
Debt outstanding	$ 150,000,000													$ 1,000,000,000							$ 0
Debt instrument, interest rate, stated percentage	5.75%	5.75%											5.75%	5.75%	5.75%	5.75%					0.00%
Debt Instrument, issuance price (in percentage)	100.25%
Face amount		$ 850,000,000
Capitalized fees and expenses		$ 15,289,000
Mortgage loan balance														$ 985,498,000							$ 0
Senior notes due 2028 \| Fair Value, Inputs, Level 1
Debt Instrument [Line Items]
Convertible debt, fair value disclosures														980,000,000
Senior notes due 2022
Debt Instrument [Line Items]
Debt outstanding														$ 0							$ 1,000,000,000
Debt instrument, interest rate, stated percentage		5.25%											5.25%	5.25%	5.25%	5.25%					5.25%
Debt redeemed	$ 1,000,000,000
Loss from debt extinguishment		$ 7,925,000
Write off of debt issuance costs		6,725,000
Tender offer net premium expense		607,000
Redemption interest expense		$ 593,000
Mortgage loan balance														$ 0							$ 991,692,000
Senior Notes
Debt Instrument [Line Items]
Debt outstanding														1,000,000,000
ESOP Loans
Debt Instrument [Line Items]
Periodic payment terms, balloon payment to be paid			$ 569,000
Debt instrument, periodic payment, principal										$ 635,000
Mortgage loan balance														30,513,000
ESOP Loans \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate			3.00%							2.91%
Capital lease - real estate
Debt Instrument [Line Items]
Debt outstanding														$ 11,564,000							$ 4,388,000
Debt instrument, interest rate, stated percentage													5.00%	5.00%	5.00%	5.00%					5.00%
Mortgage loan balance														$ 11,528,000							$ 4,333,000
Non US lines of credit
Debt Instrument [Line Items]
Debt outstanding														0							17,576,000
Remaining borrowing capacity														10,974,000		$ 15,000
Mortgage loan balance														(33,000)							$ 17,531,000
Proceeds from long-term lines of credit						$ 15,000				$ 10,974,000
Long-term line of credit, revolver outstanding balance														$ 0
Non US lines of credit \| LIBOR Rate
Debt Instrument [Line Items]
Interest rate at period end													1.46%	1.46%	1.46%	1.46%
Non US lines of credit \| Bankers Acceptance Rate
Debt Instrument [Line Items]
Interest rate at period end													1.56%	1.56%	1.56%	1.56%
Non US lines of credit \| Line of Credit One \| Northcote Holdings Pty. Ltd
Debt Instrument [Line Items]
Basis spread on variable rate				1.90%
Mortgage loan balance														$ 0
Debt instrument, interest rate, effective percentage													2.05%	2.05%	2.05%	2.05%
Term Loan May 2014 \| Northcote Holdings Pty. Ltd
Debt Instrument [Line Items]
Face amount				$ 20,000,000
Debt instrument, periodic payment, principal				1,250,000
Maximum borrowing capacity increase (decrease)				10,000,000
Medium-term Notes \| Term Loan Due 2022
Debt Instrument [Line Items]
Periodic payment terms, balloon payment to be paid				$ 9,625,000
Term Loan December 2013 and May 2014 \| Northcote Holdings Pty. Ltd
Debt Instrument [Line Items]
Basis spread on variable rate				1.95%
Long-term line of credit														$ 11,761,000	$ 17,125,000		$ 18,375,000	$ 23,375,000
Debt instrument, interest rate, effective percentage													2.09%	2.09%	2.09%	2.09%
Term loan balance change								$ 5,000,000
Mortgages \| Ames UK
Debt Instrument [Line Items]
Face amount \| £					4,000,000
Periodic payment terms, balloon payment to be paid \| £					2,500,000
Debt instrument, periodic payment, principal \| £					£ 83,000
Interest rate at period end													1.88%	1.88%	1.88%	1.88%
Forecast \| Senior notes due 2028
Debt Instrument [Line Items]
Debt redeemed												$ 150,000,000