QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Results Of Operations [Line Items]
Net sales	$ 701.3	$ 1,134.7	$ 1,101.3	$ 995.8	$ 1,107.0	$ 1,164.9	$ 1,117.5	$ 965.5	$ 3,972.8	$ 3,933.1	$ 4,354.9	$ 4,175.3
Costs of products sold	541.7	877.4	841.4	801.1	879.1	920.0	874.9	781.8	3,155.0	3,061.6	3,455.8	3,246.7
Gross profit	159.6	257.3	259.9	194.7	227.9	244.9	242.6	183.7	817.8	871.5	899.1	928.6
Selling, general and administrative expenses	126.0	157.0	161.8	157.1	146.3	152.8	155.9	134.9	535.5	601.9	589.9	510.3
Acquisition and integration related costs	1.7	1.2	2.0	2.2	2.4	2.0	11.5	2.6	17.4	7.1	18.5	19.0
Restructuring and other charges	20.1	25.2	14.6	2.7	3.8	2.7	(6.8)	5.7	2.7	62.6	5.4	18.7
Non-cash asset impairment charges	10.1	3.4	10.7	13.7	0.7	0.2	0.4	1.3	2.3	37.9	2.6	20.3
(Gain) loss on disposal of properties, plants and equipment, net	(3.8)	(2.6)	0.5	(1.6)	(2.7)	(3.4)	(0.3)	(2.7)		(7.5)	(8.8)	(2.5)
Loss (gain) on disposal of businesses, net	0.5	0.0	0.5	0.9	0.1	(46.1)	0.0	0.0	(46.1)	1.9	(46.0)	(64.0)
Operating profit	5.0	73.1	69.8	19.7	77.3	136.7	81.9	41.9	313.1	167.6	337.8	426.8
Interest expense, net	9.8	14.5	15.6	16.2	16.6	18.8	8.2	2.4	40.7	56.1	46.0	15.7
Other expense (income), net	4.8	2.8	(0.2)	0.4	0.6	0.8	(0.4)	9.1	9.9	7.8	10.1	11.2
Income (loss) before income tax expense and equity earnings of unconsolidated affiliates, net	(9.6)	55.8	54.4	3.1	60.1	117.1	74.1	30.4	262.5	103.7	281.7	396.4
Income tax (benefit) expense	26.8	11.8	23.6	2.6	6.2	33.5	21.3	(38.8)	18.9	64.8	22.2	98.1
Equity earnings of unconsolidated affiliates, net of tax	2.2	(0.7)	(0.4)	(0.4)	(1.0)	(0.9)	(0.7)	(0.5)	(2.6)	0.7	(3.1)	(2.2)
Net income from continuing operations	(38.6)	44.7	31.2	0.9	54.9	84.5	53.5	69.7	246.2	38.2	262.6	300.5
Net income (loss) 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	724.8	69.4	54.5	14.4	75.6	93.6	52.0	74.3	269.5	863.1	295.5	379.1
Net income attributable to noncontrolling interests	(4.7)	(5.4)	(7.2)	(5.8)	(5.5)	(6.5)	(7.6)	(7.1)	(25.7)	(23.1)	(26.7)	(19.9)
Net income attributable to Greif, Inc.	$ 720.1	$ 64.0	$ 47.3	$ 8.6	$ 70.1	$ 87.1	$ 44.4	$ 67.2	$ 243.8	$ 840.0	$ 268.8	$ 359.2
Earnings per Class A common stock - basic
Quarterly Results Of Operations [Line Items]
Common stock (continued operations) - basic (in usd per share)	$ (0.74)	$ 0.67	$ 0.42	$ (0.08)	$ 0.85	$ 1.35	$ 0.80	$ 1.09	$ 3.83	$ 0.27	$ 4.09	$ 4.86
Ccommon stock (discontinued operations) - basic (in usd per share)	13.14	0.43	0.40	0.23	0.36	0.16	(0.03)	0.08	0.40	14.20	0.57	1.36
Earnings per common stock - basic (in usd per share)	12.40	1.10	0.82	0.15	1.21	1.51	0.77	1.17	4.23	14.47	4.66	6.22
Common stock (continued operations) - diluted (in usd per share)	(0.73)	0.67	0.42	(0.08)	0.85	1.34	0.80	1.09	3.81	0.28	4.08	4.81
Common stock (discontinued operations) - diluted (in usd per share)	13.00	0.43	0.40	0.23	0.35	0.16	(0.03)	0.08	0.40	14.06	0.56	1.34
Earnings per common stock - diluted (in usd per share)	12.27	1.10	0.82	0.15	1.20	1.50	0.77	1.17	4.21	14.34	4.64	6.15
Earnings per Class B common stock - basic
Quarterly Results Of Operations [Line Items]
Common stock (continued operations) - basic (in usd per share)	(1.13)	1.02	0.62	(0.13)	1.29	2.02	1.19	1.63	5.72	0.38	6.13	7.28
Ccommon stock (discontinued operations) - basic (in usd per share)	19.72	0.64	0.60	0.35	0.53	0.24	(0.04)	0.12	0.61	21.31	0.85	2.04
Earnings per common stock - basic (in usd per share)	18.59	1.66	1.22	0.22	1.82	2.26	1.15	1.75	6.33	21.69	6.98	9.32
Common stock (continued operations) - diluted (in usd per share)	(1.13)	1.02	0.62	(0.13)	1.29	2.02	1.19	1.63	5.72	0.38	6.13	7.28
Common stock (discontinued operations) - diluted (in usd per share)	19.72	0.64	0.60	0.35	0.53	0.24	(0.04)	0.12	0.61	21.31	0.85	2.04
Earnings per common stock - diluted (in usd per share)	$ 18.59	$ 1.66	$ 1.22	$ 0.22	$ 1.82	$ 2.26	$ 1.15	$ 1.75	$ 6.33	$ 21.69	$ 6.98	$ 9.32