Temiscaming Operations - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 27, 2026	Mar. 28, 2026	Jun. 28, 2025	Sep. 28, 2024	Jun. 27, 2026	Jun. 28, 2025
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	$ 19,000				$ 19,000
Asset impairment	13,037		$ 0		13,037	$ 0
Permanent idling charges	0		$ 0		40,883	$ 0
High Yield Pulp
Restructuring Cost and Reserve [Line Items]
Asset impairment	13,000
Total High Purity Cellulose
Restructuring Cost and Reserve [Line Items]
Asset impairment				$ 25,000
Mothballing Costs
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	8,000				8,000
Severance and Other Employee Costs
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	6,000				6,000
Other Costs
Restructuring Cost and Reserve [Line Items]
Costs incurred to date	$ 5,000				$ 5,000
Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Permanent idling charges		$ 35,000
Other Asset Adjustment
Restructuring Cost and Reserve [Line Items]
Permanent idling charges		$ 6,000