v3.26.3
Financial Instruments and Risk Management - General (Details)
$ / shares in Units, € in Millions, shares in Millions, $ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
USD ($)
shares
approach
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
shares
approach
$ / shares
Sep. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2025
EUR (€)
Jun. 30, 2025
USD ($)
May 31, 2025
EUR (€)
Dec. 31, 2024
USD ($)
Financial Instruments and Risk Management                    
Other comprehensive earnings (loss), net of tax $ 266 $ 43 $ 333 $ 91            
Total shareholders' equity 5,740 5,452 5,740 5,452 $ 5,766 $ 5,421   $ 5,277   $ 5,930
Accumulated Other Comprehensive Earnings (Loss)                    
Financial Instruments and Risk Management                    
Other comprehensive earnings (loss), net of tax 266 43 333 91            
Total shareholders' equity (536) $ (912) (536) $ (912) $ (802) (869)   $ (955)   $ (1,003)
Accumulated Other Comprehensive Earnings (Loss) For Non Derivative Financial Instrument                    
Financial Instruments and Risk Management                    
Total shareholders' equity $ (509)   $ (509)     $ (484)        
Senior Notes 1.50%, euro denominated, due March 2027                    
Financial Instruments and Risk Management                    
Interest rate (as a percent) 1.50%   1.50%     1.50% 1.50%      
Net Investment | Accumulated Other Comprehensive Earnings (Loss)                    
Financial Instruments and Risk Management                    
Total shareholders' equity $ 12   $ 12              
Net Investment | Accumulated Other Comprehensive Earnings (Loss) For Non Derivative Financial Instrument                    
Financial Instruments and Risk Management                    
Other comprehensive earnings (loss), net of tax $ 10   $ 44              
Net Investment | 4.25% senior notes                    
Financial Instruments and Risk Management                    
Face amount of debt | €                 € 850  
Interest rate (as a percent)                 4.25%  
Net Investment | Senior Notes 1.50%, euro denominated, due March 2027                    
Financial Instruments and Risk Management                    
Face amount of debt | €             € 550      
Interest rate (as a percent)           1.50% 1.50%      
Commodity contracts                    
Financial Instruments and Risk Management                    
Number of methods through which entity manages commodity price risk in connection with market price fluctuations of aluminum ingot | approach 2   2              
Notional amount of contracts $ 2,104   $ 2,104              
Net gain (loss) included in AOCI, after-tax $ 30   30              
Net gain (loss) included in AOCI, after-tax, expected to be recognized in net earnings within the next 12 months     $ 30              
Longest duration of forecasted hedge transactions in years 2 years   2 years              
Currency                    
Financial Instruments and Risk Management                    
Notional amount of contracts $ 2,934   $ 2,934              
Net gain (loss) included in AOCI, after-tax $ (1)   (1)              
Net gain (loss) included in AOCI, after-tax, expected to be recognized in net earnings within the next 12 months     $ (1)              
Longest duration of forecasted hedge transactions in years 2 years   2 years              
Interest Rate                    
Financial Instruments and Risk Management                    
Notional amount of contracts $ 600   $ 600              
Net gain (loss) included in AOCI, after-tax $ 3   3              
Net gain (loss) included in AOCI, after-tax, expected to be recognized in net earnings within the next 12 months     $ 3              
Longest duration of forecasted hedge transactions in years 1 year   1 year              
Net Investment                    
Financial Instruments and Risk Management                    
Notional amount of contracts $ 1,050   $ 1,050              
Net gain (loss) included in AOCI, after-tax $ (58)   $ (58)              
Longest duration of forecasted hedge transactions in years 3 years   3 years              
Equity contracts                    
Financial Instruments and Risk Management                    
Combined notional value, shares | shares 0.7   0.7              
Change in company's stock price (in dollars per share) | $ / shares     $ 1