v3.26.3
ACQUISITIONS - Narrative (Details)
$ / shares in Units, € in Millions, $ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Jun. 04, 2026
USD ($)
May 18, 2026
USD ($)
Jun. 30, 2025
USD ($)
plant
Jun. 30, 2025
EUR (€)
plant
Jan. 31, 2025
USD ($)
$ / shares
shares
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Business Combination [Line Items]                    
Gain on disposition of business           $ 0 $ (16) $ 11 $ 35  
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Remedies Divestiture                    
Business Combination [Line Items]                    
Number of plants divested | plant     5 5            
Proceeds from divestiture of businesses     $ 147 € 125            
Gain on disposition of business                   $ 46
Dover Facility                    
Business Combination [Line Items]                    
Asset acquisition, consideration transferred   $ 95                
North Pacific Paper Company                    
Business Combination [Line Items]                    
Business combination, consideration transferred $ 362                  
Business combination, acquisition-related cost, expense           2   7    
Business combination, acquiree's revenue since acquisition date, actual           136   172    
Business combination, acquiree's earnings (loss) since acquisition date, actual           3   (2)    
Business combination, pro forma information, pro forma income (loss), after tax           $ (1,126) (1,113) (1,092) (1,163)  
North Pacific Paper Company | Additional Depreciation Expense On Fixed Assets                    
Business Combination [Line Items]                    
Business combination, pro forma information, pro forma income (loss), after tax             12 $ 20 36  
DS Smith Plc                    
Business Combination [Line Items]                    
Business combination, consideration transferred         $ 9,900          
Business combination, acquisition-related cost, expense             4   94  
Business combination, acquiree's revenue since acquisition date, actual             2,200   5,700  
Business combination, acquiree's earnings (loss) since acquisition date, actual             (317)   (505)  
Business combination, pro forma information, pro forma income (loss), after tax             (1,131)   (1,148)  
Number of IP shares issued for each DS Smith share (in shares) | shares         0.1285          
Business combination, consideration transferred, equity interest, share issued, number of shares (in shares) | shares         178,126,631          
Business combination, voting equity interest acquired, percentage         34.10%          
Business combination, price per share (in dollars per share) | $ / shares         $ 55.63          
DS Smith Plc | Additional Depreciation Expense On Fixed Assets                    
Business Combination [Line Items]                    
Business combination, pro forma information, pro forma income (loss), after tax                 13  
DS Smith Plc | Business Combination, Pro Forma Information, Nonrecurring Adjustment, Acquisition-Related Cost                    
Business Combination [Line Items]                    
Business combination, integration-related cost, expense             11   104  
DS Smith Plc | Business Combination, Pro Forma Information, Nonrecurring Adjustment, Inventory, Fair Value Adjustment                    
Business Combination [Line Items]                    
Business combination, pro forma information, pro forma income (loss), after tax             $ 41   30  
DS Smith Plc | Additional Amortization Expense on Identifiable Assets                    
Business Combination [Line Items]                    
Business combination, pro forma information, pro forma income (loss), after tax                 $ 16