v3.25.2
Cover - shares
6 Months Ended
Jun. 30, 2025
Jul. 31, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 001-42161  
Registrant Name Smurfit Westrock plc  
Entity Incorporation, State or Country Code L2  
Entity Tax Identification Number 98-1776979  
Entity Address, Address Line One Beech Hill, Clonskeagh  
Entity Address, City or Town Dublin 4  
Entity Address, Postal Zip Code D04 N2R2  
Entity Address, Country IE  
City Area Code +353  
Local Phone Number 1 202 7000  
Title of 12(b) Security Ordinary shares, par value $0.001 per share  
Trading Symbol SW  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   522,125,044
Central Index Key 0002005951  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Amendment Flag false