Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2025	Jun. 30, 2025
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2025
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
No Trading Symbol Flag	true
Title of 12(b) Security	None
Entity Registrant Name	Domtar Corporation
Entity Central Index Key	0001381531
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	Yes
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding	0
Entity Public Float		$ 0
ICFR Auditor Attestation Flag	false
Entity File Number	001-33164
Entity Tax Identification Number	20-5901152
Entity Address, Address Line One	234 Kingsley Park Drive
Entity Address, City or Town	Fort Mill
Entity Address, State or Province	SC
Entity Address, Postal Zip Code	29715
City Area Code	803
Local Phone Number	802-7500
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Document Financial Statement Error Correction [Flag]	false
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Montréal, Canada
Auditor Firm ID	271
Auditor Opinion	Opinion on the Financial Statements We have audited the accompanying consolidated balance sheets of Domtar Corporation and its subsidiaries (the Company) as of December 31, 2025 and 2024, and the related consolidated statements of earnings (loss) and comprehensive income (loss), of shareholders’ equity and of cash flows for each of the three years in the period ended December 31, 2025, including the related notes and schedule of valuation and qualifying accounts for each of the three years in the period ended December 31, 2025 appearing under Item 15(a)(2) (collectively referred to as the consolidated financial statements). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2025 in conformity with accounting principles generally accepted in the United States of America.
Other Address
Document Information [Line Items]
Entity Address, Address Line One	395 de Maisonneuve Blvd. West
Entity Address, City or Town	Montreal
Entity Address, State or Province	QC
Entity Address, Country	CA
Entity Address, Postal Zip Code	H3A 1L6
City Area Code	514
Local Phone Number	848-5555

Domtar CORP 10-K