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DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ / shares in Units, $ in Thousands, $ in Thousands |  |  |  | 1 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |
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Dec. 22, 2020 USD ($) | Aug. 21, 2020 USD ($) shares | Aug. 21, 2020 USD ($) shares | Aug. 18, 2020 USD ($) shares | Aug. 31, 2020 USD ($) shares | Sep. 30, 2021 USD ($) unit segment $ / shares | Dec. 31, 2020 USD ($) | Sep. 30, 2020 USD ($) unit $ / shares | Sep. 30, 2019 USD ($) | Sep. 30, 2021 AUD ($) | Nov. 12, 2020 USD ($) | Sep. 30, 2020 AUD ($) | Sep. 30, 2020 CAD ($) | Jan. 30, 2020 USD ($) | Jan. 29, 2020 USD ($) | Nov. 30, 2019 USD ($) | Oct. 01, 2019 USD ($) | Sep. 30, 2018 USD ($)
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sale of stock, number of shares issued (in shares) | shares |  | 700,000 | 8,700,000 | 8,000,000 | 8,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Net process from sale of stock |  | $ 14,335,000 | $ 178,165,000 | $ 163,830,000 | $ 178,165,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Number of reportable segments | segment |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |
Cash in non U.S. bank accounts |  |  |  |  |  | $ 65,000,000 |  | $ 55,000,000 |  |  |  |  |  |  |  |  |  |
Fair value of insurance contracts |  |  |  |  |  | 3,973,000 |  |  |  |  |  |  |  |  |  |  |  |
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax |  |  |  |  |  | 6,433,000 |  | 5,601,000 |  |  |  |  |  |  |  |  |  |
Defined benefit plan, fair value of plan assets |  |  |  |  |  | 160,523,000 |  | 147,145,000 |  |  |  |  |  |  |  |  |  |
Change in retained earnings |  |  |  |  |  | 807,158,000 |  | 700,151,000 | $ 477,763,000 |  |  |  |  |  |  |  |  | $ 474,391,000
Customer program reserves and cash discounts netted against accounts receivable |  |  |  |  |  | 49,833,000 |  | 44,439,000 |  |  |  |  |  |  |  |  |  |
Depreciation, depletion and amortization, nonproduction |  |  |  |  |  | 42,741,000 |  | 42,614,000 | 42,124,000 |  |  |  |  |  |  |  |  |
Accumulated capitalized interest costs |  |  |  |  |  | 1,592,000 |  | $ 2,098,000 | 2,410,000 |  |  |  |  |  |  |  |  |
Original cost of fully depreciated property plant and equipment |  |  |  |  |  | $ 261,101,000 |  |  |  |  |  |  |  |  |  |  |  |
Number of reporting units | unit |  |  |  |  |  | 2 |  | 3 |  |  |  |  |  |  |  |  |  |
Fair value projection, term |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |
Fair value terminal value (in percentage) |  |  |  |  |  | 3.00% |  |  |  |  |  |  |  |  |  |  |  |
Operating right-of-use assets |  |  |  |  |  | $ 144,598,000 |  | $ 154,349,000 |  |  |  |  |  |  |  |  |  |
Lease liabilities |  |  |  |  |  | 149,196,000 |  | 160,260,000 |  |  |  |  |  |  |  |  |  |
Goodwill, impairment loss |  |  |  |  |  | 0 |  | 0 | 0 |  |  |  |  |  |  |  |  |
Research and development arrangement, contract to perform for others, costs incurred, gross |  |  |  |  |  | 7,000,000 |  | 8,000,000 | 8,000,000 |  |  |  |  |  |  |  |  |
Shipping and handling cost |  |  |  |  |  | 113,700,000 |  | 100,135,000 | 93,700,000 |  |  |  |  |  |  |  |  |
Selling, general and administrative expenses |  |  |  |  |  | 470,530,000 |  | 444,454,000 | 408,339,000 |  |  |  |  |  |  |  |  |
Non-service cost components of net periodic benefit cost (credit) |  |  |  |  |  | (907,000) |  | (1,559,000) | (3,148,000) |  |  |  |  |  |  |  |  |
One Time Charges | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 65,000,000 |  |
One Time Charges | Next-generation Business Platform | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  | $ 65,000,000 |  |  |  |  |  |  |
Capital Investments | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 65,000,000 |  |
Capital Investments | Next-generation Business Platform | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  | 65,000,000 |  |  |  |  |  |  |
Employee Severance and Facility Closing | Next-generation Business Platform | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  | 46,000,000 |  |  |  |  |  |  |
Personnel Related Costs | Next-generation Business Platform | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  | 26,000,000 |  |  |  |  |  |  |
Facilities, Exit Costs and Other | Next-generation Business Platform | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  | 20,000,000 |  |  |  |  |  |  |
Asset Write-Downs | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 19,000,000 |  |
Asset Write-Downs | Next-generation Business Platform | Consumer and Professional Products |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Restructuring and related cost |  |  |  |  |  |  |  |  |  |  | $ 19,000,000 |  |  |  |  |  |  |
Quatro Design Pty Ltd |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business combination, expected annual revenue from acquiree | $ 5,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Selling, General and Administrative Expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Depreciation |  |  |  |  |  | $ 14,362,000 |  | 13,944,000 | 13,314,000 |  |  |  |  |  |  |  |  |
Home Depot |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of consolidated accounts receivable |  |  |  |  |  | 19.00% |  |  |  |  |  |  |  |  |  |  |  |
Fair Value, Inputs, Level 2 | Estimate of Fair Value Measurement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Trading securities |  |  |  |  |  | $ 16,044,000 |  | 1,703,000 |  |  |  |  |  |  |  |  |  |
Fair Value, Inputs, Level 2 | Portion at other than Fair Value Measurement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Trading securities |  |  |  |  |  | 15,050,000 |  | $ 1,000,000 |  |  |  |  |  |  |  |  |  |
Senior Notes Due 2028 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt instrument, face amount |  |  |  |  |  |  | $ 1,000,000,000 |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  | 5.75% |  |  |  |  |  |  |  |  |  |  |
Senior Notes Due 2028 | Fair Value, Inputs, Level 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt, fair value |  |  |  |  |  | $ 1,060,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes Due 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated percentage |  |  |  |  |  |  | 5.25% |  |  |  |  |  |  |  |  |  |  |
Extinguishment of debt, amount |  |  |  |  |  |  | $ 1,000,000,000 |  |  |  |  |  |  |  |  |  |  |
Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value discount rates (in percentage) |  |  |  |  |  | 7.10% |  |  |  |  |  |  |  |  |  |  |  |
Finite-lived intangible asset, useful life |  |  |  |  |  | 8 years |  |  |  |  |  |  |  |  |  |  |  |
Minimum | Building and Building Improvements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment, useful life |  |  |  |  |  | 25 years |  |  |  |  |  |  |  |  |  |  |  |
Minimum | Machinery and equipment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment, useful life |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maturity period of highly liquid investments |  |  |  |  |  | 3 months |  |  |  |  |  |  |  |  |  |  |  |
Fair value discount rates (in percentage) |  |  |  |  |  | 9.00% |  |  |  |  |  |  |  |  |  |  |  |
Finite-lived intangible asset, useful life |  |  |  |  |  | 25 years |  |  |  |  |  |  |  |  |  |  |  |
Maximum | Building and Building Improvements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment, useful life |  |  |  |  |  | 40 years |  |  |  |  |  |  |  |  |  |  |  |
Maximum | Machinery and equipment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment, useful life |  |  |  |  |  | 15 years |  |  |  |  |  |  |  |  |  |  |  |
Australian Dollar Contracts | Designated as hedging instrument |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, notional amount |  |  |  |  |  |  |  |  |  | $ 20,000 |  | $ 32,000 |  |  |  |  |  |
Contracts weighted average rate price (in dollars per share) | $ / shares |  |  |  |  |  | $ 1.27 |  | $ 1.41 |  |  |  |  |  |  |  |  |  |
Accumulated other comprehensive income (loss), foreign currency translation adjustment, before tax |  |  |  |  |  | $ 1,710,000 |  | $ 168,000 |  |  |  |  |  |  |  |  |  |
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax |  |  |  |  |  | 1,197,000 |  | 109,000 |  |  |  |  |  |  |  |  |  |
Gain (loss) on hedging activity |  |  |  |  |  | $ (2,204,000) |  | $ (2,163,000) |  |  |  |  |  |  |  |  |  |
Australian Dollar Contracts | Minimum | Designated as hedging instrument |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contracts expiration days |  |  |  |  |  | 29 days |  |  |  |  |  |  |  |  |  |  |  |
Australian Dollar Contracts | Maximum | Designated as hedging instrument |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contracts expiration days |  |  |  |  |  | 90 days |  |  |  |  |  |  |  |  |  |  |  |
Canadian Dollar Contract | Not Designated as Hedging Instrument |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, notional amount |  |  |  |  |  | $ 4,600,000 |  |  |  |  |  |  | $ 7,900 |  |  |  |  |
Contracts weighted average rate price (in dollars per share) | $ / shares |  |  |  |  |  | $ 1.26 |  | $ 1.32 |  |  |  |  |  |  |  |  |  |
Fair value gain (loss) on foreign currency contract not qualify for hedge accounting |  |  |  |  |  | $ 38,000 |  | $ (92,000) |  |  |  |  |  |  |  |  |  |
Canadian Dollar Contract | Fair Value, Inputs, Level 2 | Not Designated as Hedging Instrument | Other Income |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on sale of derivatives |  |  |  |  |  | $ (381,000) |  | 189,000 |  |  |  |  |  |  |  |  |  |
Canadian Dollar Contract | Minimum | Not Designated as Hedging Instrument |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of contract |  |  |  |  |  | 30 days |  |  |  |  |  |  |  |  |  |  |  |
Canadian Dollar Contract | Maximum | Not Designated as Hedging Instrument |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of contract |  |  |  |  |  | 360 days |  |  |  |  |  |  |  |  |  |  |  |
Great Britain Pound Contracts | Not Designated as Hedging Instrument |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, notional amount |  |  |  |  |  | $ 0 |  | 5,400,000 |  |  |  |  |  |  |  |  |  |
Fair value gain (loss) on foreign currency contract not qualify for hedge accounting |  |  |  |  |  | 30,000 |  | 39,000 |  |  |  |  |  |  |  |  |  |
Great Britain Pound Contracts | Fair Value, Inputs, Level 2 | Not Designated as Hedging Instrument | Other Income |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on sale of derivatives |  |  |  |  |  | 494,000 |  | $ 0 |  |  |  |  |  |  |  |  |  |
Great Britain Pound Contracts | Maximum | Not Designated as Hedging Instrument |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contracts weighted average rate price (in dollars per share) | $ / shares |  |  |  |  |  |  |  | $ 0.77 |  |  |  |  |  |  |  |  |  |
Foreign currency translation adjustments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in retained earnings |  |  |  |  |  | (19,250,000) |  | $ (25,683,000) |  |  |  |  |  |  |  |  |  |
Shipping and Handling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Selling, general and administrative expenses |  |  |  |  |  | 58,100,000 |  | 54,500,000 | 53,500,000 |  |  |  |  |  |  |  |  |
Advertising |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Selling, general and administrative expenses |  |  |  |  |  | $ 19,000,000 |  | $ 18,000,000 | $ 18,000,000 |  |  |  |  |  |  |  |  |
Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in retained earnings |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (5,618,000)
Operating right-of-use assets |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 163,552,000 |
Lease liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 163,676,000 |
Revolver Due 2025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Description Of Business And Summary Of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 400,000,000 | $ 350,000,000 |  |  |

X
- Definition Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Before Tax + References No definition available. + Details
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X
- Definition Business Combination, Expected Annual Revenue From Acquiree + References No definition available. + Details
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Namespace Prefix: | gff_
Data Type: | xbrli:monetaryItemType
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X
- Definition Amount of cash in non-U.S bank accounts as of the reporting date. + References No definition available. + Details
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