Quarterly Financial Data (Unaudited) - Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016
Quarterly Results Of Operations [Line Items]
Total net sales	$ 987.7	$ 1,012.1	$ 968.3	$ 905.7	$ 968.1	$ 961.8	$ 887.4	$ 820.9	$ 3,873.8	$ 3,638.2	$ 3,323.6
Gross profit	204.8	217.1	195.3	171.7	182.4	187.1	181.9	163.3	788.9	714.7	684.9
Net income	45.5	72.0	51.9	60.1	39.7	47.5	39.9	8.0	229.5	135.1	75.5
Net income attributable to Greif, Inc.	40.1	$ 67.7	$ 45.1	$ 56.5	33.3	$ 43.9	$ 36.0	$ 5.4	209.4	118.6	74.9
Diluted:
Restructuring charges	4.8				4.0				18.6	12.7	26.9
Non-cash asset impairment charges	4.2				14.9				8.3	20.8	51.4
Pension settlement charge	0.9				1.5					25.9
Gain on disposals of properties, plants and equipment, net	1.9				3.5				$ (5.6)	$ (0.4)	$ (10.3)
Gain (Loss) on sale of business	$ 0.9				$ (3.9)
Class A Common Stock
Basic earnings per share attributable to Greif, Inc.:
EPS Basic (usd per share)	$ 0.68	$ 1.15	$ 0.77	$ 0.96	$ 0.57	$ 0.74	$ 0.61	$ 0.10	$ 3.56	$ 2.02	$ 1.28
Diluted earnings per share attributed to Greif, Inc.:
EPS Diluted (usd per share)	$ 0.67	$ 1.15	$ 0.77	$ 0.96	$ 0.57	$ 0.74	$ 0.61	$ 0.10	$ 3.55	$ 2.02	$ 1.28
Basic:
Basic (shares)	25,941,279	25,941,279	25,934,680	25,845,758	25,835,281	25,834,636	25,824,194	25,787,769	25,915,887	25,820,470	25,755,545
Diluted:
Diluted (shares)	26,139,524	25,941,279	25,934,680	25,845,758	25,835,281	25,835,294	25,828,882	25,792,441	25,965,856	25,822,940	25,756,893
Market price of common stock (usd per share)	$ 47.30	$ 54.03	$ 57.63	$ 57.76	$ 55.53	$ 55.68	$ 57.75	$ 56.28
Class B Common Stock
Basic earnings per share attributable to Greif, Inc.:
EPS Basic (usd per share)	1.03	1.72	1.14	1.44	0.85	1.12	0.92	0.13	$ 5.33	$ 3.02	$ 1.90
Diluted earnings per share attributed to Greif, Inc.:
EPS Diluted (usd per share)	$ 1.03	$ 1.72	$ 1.14	$ 1.44	$ 0.85	$ 1.12	$ 0.92	$ 0.13	$ 5.33	$ 3.02	$ 1.90
Basic:
Basic (shares)	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,009,596	22,009,725	22,009,725	22,000,000	22,000,000	22,100,000
Diluted:
Diluted (shares)	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,009,596	22,009,725	22,009,725	22,000,000	22,000,000	22,100,000
Market price of common stock (usd per share)	$ 51.36	$ 57.20	$ 61.56	$ 61.6	$ 62.85	$ 59.26	$ 65.92	$ 68.94
Maximum | Class A Common Stock
Diluted:
Market price of common stock (usd per share)	58.82	60.89	59.09	62.94	60.01	60.32	58.95	57.72
Maximum | Class B Common Stock
Diluted:
Market price of common stock (usd per share)	63.5	64.02	63.52	68.71	65.25	66.6	71.31	70.2
Minimum | Class A Common Stock
Diluted:
Market price of common stock (usd per share)	44.72	51.71	48.80	49.68	55	53.55	51.70	44.22
Minimum | Class B Common Stock
Diluted:
Market price of common stock (usd per share)	$ 48.35	$ 56.01	$ 52.07	$ 55.90	$ 57.58	$ 54.81	$ 56.93	$ 55.05