v3.26.1
Segments - Schedule of Segment Reporting Information, by Segment (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 28, 2026
Mar. 29, 2025
Segment Reporting Information [Line Items]    
Net sales $ 319,065 $ 352,584
Operating Segments    
Segment Reporting Information [Line Items]    
Net sales 318,994 352,524
Operating Segments | Total High Purity Cellulose    
Segment Reporting Information [Line Items]    
Net sales 262,901 278,639
Operating Segments | Cellulose Specialties    
Segment Reporting Information [Line Items]    
Net sales 148,072 194,552
Operating Segments | Cellulose Commodities    
Segment Reporting Information [Line Items]    
Net sales 102,211 72,842
Operating Segments | Biomaterials and other    
Segment Reporting Information [Line Items]    
Net sales 12,618 11,245
Operating Segments | Total Paperboard & High Yield Pulp    
Segment Reporting Information [Line Items]    
Net sales 56,093 73,885
Operating Segments | Paperboard    
Segment Reporting Information [Line Items]    
Net sales 41,726 49,193
Operating Segments | High Yield Pulp    
Segment Reporting Information [Line Items]    
Net sales 14,367 24,692
Corporate & Other    
Segment Reporting Information [Line Items]    
Net sales $ 71 $ 60