v3.26.3
Supplemental Information (Additional Information) (Details)
€ in Millions, $ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2026
USD ($)
Jun. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Aug. 15, 2026
EUR (€)
Related Party Transaction [Line Items]                  
Other assets, net $ 734       $ 734   $ 784    
Deferred turnaround costs, net 369       369   433    
Accrued Liabilities and Other Liabilities [Abstract]                  
Accrued and other liabilities 1,513       1,513   1,490    
Accrued rebates 288       288   225    
Operating lease liabilities, current 134       134   138    
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs 58     $ 17 79 $ 139      
Payments for Hedge, Investing Activities         175 0      
Proceeds from settlement of foreign currency swap agreements         182 0      
Currency Swap | Net Investment Hedging                  
Restructuring Charges [Abstract]                  
Derivative, Notional Amount | €                 € 150
Payments for Hedge, Investing Activities         175        
Proceeds from settlement of foreign currency swap agreements         182        
Pernis Facility Closure                  
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs (3) $ (4) $ 4 $ 15   $ 130 247 $ 75  
Pernis Facility Closure | Inventory Write-Down [Member]                  
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs             15    
Pernis Facility Closure | Employee Severance [Member]                  
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs 1 1 2            
Expected restructuring charges remaining 3       3        
Pernis Facility Closure | Facility Closing [Member]                  
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs 0 (2) (2)            
Chlorovinyls and Styrene Facility Closure                  
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs 7 7 11       393    
Chlorovinyls and Styrene Facility Closure | Inventory Write-Down [Member]                  
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs             30    
Chlorovinyls and Styrene Facility Closure | Employee Severance [Member]                  
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs 0 $ 1 $ 3            
Expected restructuring charges remaining 1       1        
Chlorovinyls and Styrene Facility Closure | Accelerated Depreciation and Amortization                  
Restructuring Charges [Abstract]                  
Restructuring, transaction and integration-related costs             287    
Chlorovinyls and Styrene Facility Closure | Facility Closing [Member]                  
Restructuring Charges [Abstract]                  
Expected restructuring charges remaining 2       2        
Related Party                  
Accrued Liabilities and Other Liabilities [Abstract]                  
Other liabilities, current $ 21       $ 21   $ 31    
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01                  
Related Party Transaction [Line Items]                  
Remaining performance obligation term 20 years       20 years        
Remaining performance obligations $ 182       $ 182