v3.26.1
Segments- Significant Operating Expenses (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 28, 2026
Mar. 29, 2025
Segment Reporting Information [Line Items]    
Total consolidated net sales $ 319,065 $ 352,584
Total segment cost of sales 326,658 328,530
Selling, general and administrative expense 19,171 23,259
Temiscaming HPC permanent idling charges - other asset adjustments 40,883 0
Operating loss (65,315) (15,093)
Interest expense (23,114) (23,603)
Components of pension and OPEB, excluding service costs 1,033 632
Other expense, net (952) 892
Loss before income tax (88,348) (37,172)
Other segment items    
Depreciation and amortization 33,453 31,251
Temiscaming HPC permanent idling charges - accelerated depreciation 34,494 0
Total consolidated depreciation and amortization 67,947  
Operating Segments    
Segment Reporting Information [Line Items]    
Total consolidated net sales 318,994 352,524
Total segment cost of sales 326,552 328,278
Operating loss (53,382) 11,500
Other segment items    
Depreciation and amortization 32,047 30,910
Temiscaming HPC permanent idling charges - accelerated depreciation 34,494  
Total consolidated depreciation and amortization 66,541  
Operating Segments | High Purity Cellulose    
Segment Reporting Information [Line Items]    
Total consolidated net sales 262,901 278,639
Key input costs (wood, chemicals, energy) 109,404 112,100
Fixed and other costs of sales 152,858 137,461
Total segment cost of sales 262,262 249,561
Selling, general and administrative expense 6,071 7,764
Temiscaming HPC permanent idling charges - other asset adjustments 40,883  
Other segment items (3,132) 1,019
Operating loss (43,183) 20,295
Other segment items    
Depreciation and amortization 28,100 25,083
Temiscaming HPC permanent idling charges - accelerated depreciation 34,494  
Total consolidated depreciation and amortization 62,594  
Operating Segments | Paperboard & High Yield Pulp    
Segment Reporting Information [Line Items]    
Total consolidated net sales 56,093 73,885
Key input costs (wood, chemicals, energy) 30,924 48,536
Fixed and other costs of sales 33,366 30,181
Total segment cost of sales 64,290 78,717
Selling, general and administrative expense 1,985 3,492
Temiscaming HPC permanent idling charges - other asset adjustments 0  
Other segment items 17 471
Operating loss (10,199) (8,795)
Other segment items    
Depreciation and amortization 3,947 5,827
Temiscaming HPC permanent idling charges - accelerated depreciation 0  
Total consolidated depreciation and amortization 3,947  
Corporate & Other    
Segment Reporting Information [Line Items]    
Total consolidated net sales 71 60
Operating loss (11,933) (26,593)
Other segment items    
Depreciation and amortization   $ 341
Total consolidated depreciation and amortization $ 1,406