Earnings Per Share - Computation of Earnings Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2017
Numerator for basic and diluted EPS
Net income attributable to Greif	$ 65.0	$ 62.7	$ 13.6	$ 29.7	$ 40.1	$ 67.7	$ 45.1	$ 56.5	$ 171.0	$ 209.4	$ 118.6
Cash dividends									104.0	100.0	98.6
Undistributed net income (loss) attributable to Greif, Inc.									$ 67.0	$ 109.4	$ 20.0
Class A common stock
Denominator for basic EPS
Denominator for basic EPS (shares)	26,257,943	26,257,943	26,250,460	25,991,433	25,941,279	25,941,279	25,934,680	25,845,758	26,189,445	25,915,887	25,820,470
Denominator for diluted EPS
Denominator for diluted EPS (shares)	26,360,148	26,257,943	26,255,112	25,991,433	26,139,524	25,941,279	25,934,680	25,845,758	26,215,111	25,965,856	25,822,940
Basic:
EPS Basic (usd per share)	$ 1.09	$ 1.06	$ 0.23	$ 0.51	$ 0.68	$ 1.15	$ 0.77	$ 0.96	$ 2.89	$ 3.56	$ 2.02
EPS Diluted
EPS Diluted (usd per share)	$ 1.09	$ 1.06	$ 0.23	$ 0.51	$ 0.67	$ 1.15	$ 0.77	$ 0.96	$ 2.89	$ 3.55	$ 2.02
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	22,007,725	22,007,725	22,007,725	22,000,000.0	22,000,000.0	22,000,000.0
Denominator for diluted EPS
Denominator for diluted EPS (shares)	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,007,725	22,000,000.0	22,000,000.0	22,000,000.0
Basic:
EPS Basic (usd per share)	$ 1.65	$ 1.59	$ 0.34	$ 0.75	$ 1.03	$ 1.72	$ 1.14	$ 1.44	$ 4.33	$ 5.33	$ 3.02
EPS Diluted
EPS Diluted (usd per share)	$ 1.65	$ 1.59	$ 0.34	$ 0.75	$ 1.03	$ 1.72	$ 1.14	$ 1.44	$ 4.33	$ 5.33	$ 3.02