Quarterly Financial Data (Unaudited) - Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
Quarterly Results Of Operations [Line Items]
Net sales	$ 1,161.3	$ 1,083.0	$ 1,158.3	$ 1,112.4	$ 1,232.1	$ 1,252.6	$ 1,213.3	$ 897.0	$ 4,515.0	$ 4,595.0	$ 3,873.8
Gross profit	231.7	219.7	240.7	222.6	259.0	279.4	248.7	172.8	914.7	959.9	788.9
Net income	48.0	24.4	15.8	36.1	69.8	67.5	21.1	35.8	124.3	194.2	229.5
Net income attributable to Greif, Inc.	44.4	$ 20.7	$ 11.4	$ 32.3	65.0	$ 62.7	$ 13.6	$ 29.7	108.8	171.0	209.4
Diluted:
Acquisition-related costs	3.5				7.5				17.0	29.7	0.7
Restructuring charges	11.9				5.8				38.7	26.1	18.6
Non-cash asset impairment charges	1.6				5.7				18.5	7.8	8.3
Gain on disposals of properties, plants and equipment, net	(17.1)				(6.8)				$ (19.2)	$ (13.9)	$ (5.6)
Gain (Loss) on sale of business	$ 0.9				$ 0.7
Class A common stock
Basic:
Basic (usd per share)	$ 0.74	$ 0.35	$ 0.19	$ 0.55	$ 1.09	$ 1.06	$ 0.23	$ 0.51	$ 1.83	$ 2.89	$ 3.56
Diluted:
Diluted (usd per share)	$ 0.74	$ 0.35	$ 0.19	$ 0.55	$ 1.09	$ 1.06	$ 0.23	$ 0.51	$ 1.83	$ 2.89	$ 3.55
Basic:
Basic (shares)	26,441,986	26,441,986	26,386,439	26,260,943	26,257,943	26,257,943	26,250,460	25,991,433	26,382,838	26,189,445	25,915,887
Diluted:
Diluted (shares)	26,512,331	26,442,595	26,386,439	26,414,280	26,360,148	26,257,943	26,255,112	25,991,433	26,390,643	26,215,111	25,965,856
Market price of common stock (usd per share)	$ 40.59	$ 34.38	$ 33.08	$ 38.77	$ 39.17	$ 34.57	$ 38.59	$ 37.67
Class B common stock
Basic:
Basic (usd per share)	1.12	0.52	0.29	0.81	1.65	1.59	0.34	0.75	$ 2.74	$ 4.33	$ 5.33
Diluted:
Diluted (usd per share)	$ 1.12	$ 0.52	$ 0.29	$ 0.81	$ 1.65	$ 1.59	$ 0.34	$ 0.75	$ 2.74	$ 4.33	$ 5.33
Basic:
Basic (shares)	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,000,000.0	22,000,000.0	22,000,000.0
Diluted:
Diluted (shares)	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,000,000.0	22,000,000.0	22,000,000.0
Market price of common stock (usd per share)	$ 43.25	$ 38.67	$ 38.50	$ 45.05	$ 47.03	$ 42.39	$ 47.23	$ 43.18
Maximum | Class A common stock
Diluted:
Market price of common stock (usd per share)	43.82	40.56	40.82	44.63	40.59	39.15	41.49	49.28
Maximum | Class B common stock
Diluted:
Market price of common stock (usd per share)	47.19	43.65	48.45	51.40	48.76	47.69	48.57	50.55
Minimum | Class A common stock
Diluted:
Market price of common stock (usd per share)	34.44	27.57	24.10	38.64	30.05	30.74	37.10	31.22
Minimum | Class B common stock
Diluted:
Market price of common stock (usd per share)	$ 38.29	$ 34.94	$ 30.80	$ 45.05	$ 37.96	$ 41.10	$ 42.48	$ 36.87