Earnings Per Share - Computation of Earnings Per Share Basic and Diluted (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
Numerator for basic and diluted EPS
Net income attributable to Greif	$ 40.1	$ 67.7	$ 45.1	$ 56.5	$ 33.3	$ 43.9	$ 36.0	$ 5.4	$ 209.4	$ 118.6	$ 74.9
Cash dividends									100.0	98.6	98.7
Undistributed net income (loss) attributable to Greif, Inc.									$ 109.4	$ 20.0	$ (23.8)
Class A Common Stock
Denominator for basic EPS
Denominator for basic EPS (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
Denominator for diluted EPS
Denominator for diluted EPS (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
EPS Basic
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
EPS Diluted
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
Class B Common Stock
Denominator for basic EPS
Denominator for basic EPS (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
Denominator for diluted EPS
Denominator for diluted EPS (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
EPS Basic
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
EPS Diluted
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