v3.26.1
Segment Information - Selected Financial Information by Reportable Segment (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Segment Reporting Information [Line Items]          
Net sales $ 2,489.9 $ 2,171.3 $ 4,857.6 $ 4,312.3  
Operating Income (Loss) [1] 291.2 333.7 542.5 614.0  
Other segment items [1],[2] 0.0 0.0 0.0 0.0  
Non-operating pension expense 1.1 0.0 2.2 0.0  
Interest expense, net (33.3) (13.1) (66.0) (26.0)  
Income before taxes 259.0 320.6 478.7 588.0  
Depreciation, amortization, and depletion 176.3 140.7 401.5 278.6  
Capital expenditures [3] 205.9 169.7 370.6 317.8  
Assets 11,015.5 9,041.2 11,015.5 9,041.2 $ 10,725.5
Variable Costs [Member]          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1] 0.0 [4] 0.0 0.0 [4] 0.0 [4]  
Fixed Costs [Member]          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1],[5] 0.0 0.0 0.0 0.0  
Freight          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1] 0.0 0.0 0.0 0.0  
Operating Segments          
Segment Reporting Information [Line Items]          
Net sales 2,531.5 2,210.1 4,937.9 4,391.1  
Operating Segments | Trade          
Segment Reporting Information [Line Items]          
Net sales 2,489.9 2,171.3 4,857.6 4,312.3  
Operating Segments | Intersegment          
Segment Reporting Information [Line Items]          
Net sales 41.6 38.8 80.3 78.8  
Elimination of intersegment sales          
Segment Reporting Information [Line Items]          
Net sales (41.6) (38.8) (80.3) (78.8)  
Packaging          
Segment Reporting Information [Line Items]          
Net sales 2,311.3 2,005.9 4,499.8 3,976.3  
Operating Income (Loss) [1] 313.2 346.3 573.5 624.4  
Other segment items [1],[2] (96.1) (55.9) (184.8) (142.9)  
Depreciation, amortization, and depletion 166.3 131.8 382.2 260.1  
Capital expenditures [3] 198.7 165.0 361.4 296.1  
Assets 9,676.6 7,418.6 9,676.6 7,418.6  
Packaging | Variable Costs [Member]          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1] (1,110.6) [4] (960.1) (2,139.0) [4] (1,921.2) [4]  
Packaging | Fixed Costs [Member]          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1],[5] (522.7) (445.2) (1,093.9) (892.7)  
Packaging | Trade          
Segment Reporting Information [Line Items]          
Net sales 2,309.3 2,005.9 4,497.0 3,976.3  
Packaging | Intersegment          
Segment Reporting Information [Line Items]          
Net sales 2.0 0.0 2.8    
Packaging | Freight          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1] (268.7) (198.4) (508.6) (395.1)  
Packaging | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales 2,311.3 2,005.9 4,499.8 3,976.3  
Paper          
Segment Reporting Information [Line Items]          
Net sales 157.3 145.8 317.2 300.0  
Operating Income (Loss) [1] 34.3 25.8 67.2 61.4  
Other segment items [1],[2] 0.1 (0.2) (0.4) (0.3)  
Depreciation, amortization, and depletion 4.8 4.5 9.6 9.1  
Capital expenditures [3] 3.2 1.0 4.8 1.8  
Assets 399.8 405.3 399.8 405.3  
Paper | Variable Costs [Member]          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1] (83.2) [4] (82.8) (171.9) [4] (165.7) [4]  
Paper | Fixed Costs [Member]          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1],[5] (21.0) (21.8) (40.0) (40.6)  
Paper | Trade          
Segment Reporting Information [Line Items]          
Net sales 157.3 145.8 317.2 300.0  
Paper | Intersegment          
Segment Reporting Information [Line Items]          
Net sales 0.0 0.0      
Paper | Freight          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1] (18.9) (15.2) (37.7) (32.0)  
Paper | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales 157.3 145.8 317.2 300.0  
Corporate and Other          
Segment Reporting Information [Line Items]          
Net sales 21.3 19.6 40.6 36.0  
Operating Income (Loss) [1],[6] (56.3) (38.4) (98.2) (71.8)  
Other segment items [1],[2] (119.2) (96.8) (219.1) (186.6)  
Depreciation, amortization, and depletion 5.2 4.4 9.7 9.4  
Capital expenditures [3] 4.0 3.7 4.4 19.9  
Assets 939.1 1,217.3 939.1 1,217.3  
Corporate and Other | Variable Costs [Member]          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1] 0.0 [4] 0.0 0.0 [4] 0.0 [4]  
Corporate and Other | Fixed Costs [Member]          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1],[5] 0.0 0.0 0.0 0.0  
Corporate and Other | Trade          
Segment Reporting Information [Line Items]          
Net sales [7] 23.3 19.6 43.4 36.0  
Corporate and Other | Intersegment          
Segment Reporting Information [Line Items]          
Net sales 39.6 38.8 77.5 78.8  
Corporate and Other | Freight          
Segment Reporting Information [Line Items]          
Operating Income (Loss) [1] 0.0 0.0 0.0 0.0  
Corporate and Other | Operating Segments          
Segment Reporting Information [Line Items]          
Net sales $ 62.9 $ 58.4 $ 120.9 $ 114.8  
[1] The significant expense categories align with the segment-level information that is regularly provided to the CODM.
[2] Other segment items for each reportable segment primarily include:
1.
Packaging: farmout purchases, certain divisional allocations, and other expense/income items.
2.
Paper: other expense/income items.
3.
Corporate and Other: unallocated corporate costs, transportation business activity, and activity related to LTP.
[3] Includes “Additions to property, plant, and equipment” and excludes cash used for “Acquisition of business, net of cash acquired” as reported on our Consolidated Statements of Cash Flows.
[4] For the Packaging segment, primarily includes expense items for liner consumption, purchased sheets usage, medium consumption, hourly-employee related expenses and benefits, and raw materials. For the Paper segment, primarily includes expense items for chemicals, raw materials, finishing materials, hourly-employee related expenses, and repair service and materials.
[5] For both the Packaging and Paper segments, primarily includes expense items for depreciation, salaried employee-related expenses, and professional services.
[6] The significant expense categories reported for the Packaging and Paper segments are not used for Corporate and Other in the segment-level information that is regularly reviewed by the CODM. The CODM makes resource allocation decisions for Corporate and Other based on divisional income (loss) from operations.
[7] The Corporate and Other segment sales to external customers is presented net of total company intersegment eliminations.