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Reduction of workforce.

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Amount of loss from impairment of right-of-use asset from operating lease.

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Closure and Restructuring and Impairment of Long-Lived Assets - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	May 31, 2026 Employee T	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Dec. 31, 2025 USD ($)
Restructuring Cost And Reserve [Line Items]
Asset Impairment Charges		$ 2	$ 0	$ 27	$ 12
Property, Plant and Equipment [Member]
Restructuring Cost And Reserve [Line Items]
Long-lived assets impairment charges		0		6
Operating Lease Right-of-Use Assets [Member]
Restructuring Cost And Reserve [Line Items]
Long-lived assets impairment charges		2		9
Pulp and Tissue [Member]
Restructuring Cost And Reserve [Line Items]
Asset Impairment Charges		1		1
Wood Products [Member]
Restructuring Cost And Reserve [Line Items]
Asset Impairment Charges		0		6
Paper And Packaging [Member]
Restructuring Cost And Reserve [Line Items]
Asset Impairment Charges		1		6
Corporate Segment and Other Operating Segment [Member]
Restructuring Cost And Reserve [Line Items]
Asset Impairment Charges		0		2
Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Severance and termination costs		0	1	4	1
Other cost		10	1	0	1
Idling and Sale of Espanola, Ontario Mill [Member] \| Espanola, Ontario mill [Member]
Restructuring Cost And Reserve [Line Items]
Asset Impairment Charges			0		12
Catalyst Restructuring And Impairment Costs [Member] \| Catalyst British Columbia Mills [Member]
Restructuring Cost And Reserve [Line Items]
Accelerated depreciation			$ 5		$ 7
Other cost		1		2		$ 0
Write-off inventory		0		2		$ 0
Idling of Coosa Pines Alabama Mill [Member]
Restructuring Cost And Reserve [Line Items]
Reduction in annual market pulp production capacity \| T	270,000
Reduction of workforce \| Employee	285
Idling of Coosa Pines Alabama Mill [Member] \| Coosa Pines, Alabama Mill [Member]
Restructuring Cost And Reserve [Line Items]
Asset Impairment Charges		0		9
Write-off of operating lease right-of-use assets		0		3
Severance and termination costs		1		8
Other cost		3		3
Write-off inventory		$ 2		$ 12