v3.25.3

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2025	Oct. 31, 2025
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 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		522,186,327
Central Index Key	0002005951
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q3
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Cover page.

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Indicate number of shares or other units outstanding of each of registrant's classes of capital or common stock or other ownership interests, if and as stated on cover of related periodic report. Where multiple classes or units exist define each class/interest by adding class of stock items such as Common Class A [Member], Common Class B [Member] or Partnership Interest [Member] onto the Instrument [Domain] of the Entity Listings, Instrument.

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Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

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Boolean flag that is true when the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).

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Boolean flag that is true when the registrant is a shell company as defined in Rule 12b-2 of the Exchange Act.

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The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

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Local phone number for entity.

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Title of a 12(b) registered security.

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Smurfit Westrock plc 10-Q