Document and Entity Information - shares	9 Months Ended
	Jun. 30, 2019	Jul. 19, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	WRK
Entity Registrant Name	WestRock Co
Entity Central Index Key	0001732845
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		257,341,556
Entity Current Reporting Status	Yes
Entity File Number	001-38736
Entity Tax Identification Number	371880617
Entity Address, Address Line One	1000 Abernathy Road NE
Entity Address, City or Town	Atlanta
Entity Address, State or Province	Georgia
Entity Address, Postal Zip Code	30328
City Area Code	770
Local Phone Number	448-2193