DISCONTINUED OPERATIONS - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Jun. 30, 2026	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2026
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Possible tax loss				$ 8,451
Loss consists of write-down				14,332
Estimated costs to sell				8,316
Acquisition costs				5,287
Depreciation and amortization expense	$ 6,381	$ 5,951		12,239	$ 11,829
Carrying value of credit and debt card receivables	31,099			31,099
Forecast \| Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from organization of joint venture			$ 100,000
Notes issued			$ 161,100
ONCAP \| Forecast \| Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity interest (as percent)						57.00%
Griffon \| Forecast \| Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity interest (as percent)						43.00%
Cost of goods and services
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-cash charges				11,577
Assets of discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-cash charges				15,751
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-cash charges				21,282
Discontinued Operations \| Personnel related costs
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments for restructuring				6,046
Discontinued Operations \| Intangible Asset Impairments
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-cash charges				6,609
Discontinued Operations \| Inventory Write-down
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-cash charges				7,340
Global Sourcing Strategy Expansion \| Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Restructuring charges				27,328
Global Sourcing Strategy Expansion \| Discontinued Operations \| Fixed Asset Write-down Charges
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Non-cash charges				7,333
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation and amortization expense	2,389			8,574
Depreciation if not discontinued	5,965			12,150
Depreciation and amortization excluded	3,576			3,576
Depreciation and amortization expense		6,058			12,173
Amortization	1,451			5,762
Lease amortization excluded	2,931			2,931
Amortization if not discontinued	$ 4,382	$ 4,180		$ 8,693	$ 8,512

GRIFFON CORP 10-Q