Document and Entity Information - USD ($)	12 Months Ended
	Oct. 31, 2020	Dec. 14, 2020	Apr. 30, 2020
Document Information [Line Items]
Entity Address, Postal Zip Code	43015
Entity Address, State or Province	OH
Entity Address, City or Town	Delaware
Entity Address, Address Line One	425 Winter Road
Entity Tax Identification Number	31-4388903
Entity Incorporation, State or Country Code	DE
Document Transition Report	false
Document Quarterly Report	true
Document Type	10-K
Amendment Flag	false
Document Period End Date	Oct. 31, 2020
Entity File Number	001-00566
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	GREIF, INC
Entity Central Index Key	0000043920
Current Fiscal Year End Date	--10-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
City Area Code	740
Local Phone Number	549-6000
Documents Incorporated by Reference	1. The Registrant’s Definitive Proxy Statement for use in connection with the Annual Meeting of Stockholders to be held on February 23, 2021 (the “2021 Proxy Statement”), portions of which are incorporated by reference into Parts II and III of this Form 10-K. The 2021 Proxy Statement will be filed within 120 days of October 31, 2020.
ICFR Auditor Attestation Flag	true
Class A common stock
Document Information [Line Items]
Security Exchange Name	NYSE
Title of 12(b) Security	Class A Common Stock
Trading Symbol	GEF
Entity Common Stock, Shares Outstanding		26,444,986
Entity Public Float			$ 860,619,382
Class B common stock
Document Information [Line Items]
Security Exchange Name	NYSE
Title of 12(b) Security	Class B Common Stock
Trading Symbol	GEF-B
Entity Common Stock, Shares Outstanding		22,007,725
Entity Public Float			$ 234,235,302