ACQUISITIONS AND DIVESTITURES - Results from Operations from Discontinued Operations (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended							10 Months Ended	11 Months Ended	12 Months Ended
	Sep. 30, 2025	Jul. 31, 2025	Apr. 30, 2025	Jan. 31, 2025	Oct. 31, 2024	Jul. 31, 2024	Apr. 30, 2024	Jan. 31, 2024	Sep. 30, 2024	Sep. 30, 2025	Oct. 31, 2024	Oct. 31, 2023
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net income from discontinued operations, net tax	$ 763.4	$ 24.7	$ 23.3	$ 13.5	$ 20.7	$ 9.1	$ (1.5)	$ 4.6	$ 23.3	$ 824.9	$ 32.9	$ 78.6
Net income from discontinued operations attributable to Greif, Inc.										824.9	32.9	$ 78.6
Discontinued Operations, Held-for-Sale | Greif Containerboard Solutions, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales										975.7	1,093.2
Cost of products sold										770.9	921.5
Gross profit										204.8	171.7
Selling, general and administrative expenses										37.7	44.6
(Gain) loss on disposal of businesses, net										(1,096.8)	0.3
Operating profit										1,263.9	126.8
Interest expense, net										67.8	88.9
Income from discontinued operations before income tax expense and equity earnings of unconsolidated affiliates, net										1,196.1	37.9
Income tax expense										371.2	5.0
Net income from discontinued operations, net tax										824.9	32.9
Net income from discontinued operations attributable to Greif, Inc.										$ 824.9	$ 32.9