v3.26.1
Financial Instruments and Risk Management - General (Details)
$ / shares in Units, € in Millions, shares in Millions, $ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
USD ($)
shares
approach
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
shares
approach
$ / shares
Jun. 30, 2025
USD ($)
Mar. 31, 2026
USD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2025
EUR (€)
May 31, 2025
EUR (€)
Mar. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Financial Instruments and Risk Management                    
Other comprehensive earnings (loss), net of tax $ 64 $ (13) $ 67 $ 48            
Total shareholders' equity 5,766 5,277 5,766 5,277 $ 5,619 $ 5,421     $ 5,569 $ 5,930
Accumulated Other Comprehensive Earnings (Loss)                    
Financial Instruments and Risk Management                    
Other comprehensive earnings (loss), net of tax 64 (13) 67 48            
Total shareholders' equity (802) $ (955) (802) $ (955) $ (866) (869)     $ (942) $ (1,003)
Accumulated Other Comprehensive Earnings (Loss) For Non Derivative Financial Instrument                    
Financial Instruments and Risk Management                    
Total shareholders' equity $ (493)   $ (493)     $ (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 $ 1   $ 1              
Net Investment | Accumulated Other Comprehensive Earnings (Loss) For Non Derivative Financial Instrument                    
Financial Instruments and Risk Management                    
Other comprehensive earnings (loss), net of tax $ 14   $ 34              
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 $ 1,877   $ 1,877              
Net gain (loss) included in AOCI, after-tax $ 89   89              
Net gain (loss) included in AOCI, after-tax, expected to be recognized in net earnings within the next 12 months     $ 89              
Longest duration of forecasted hedge transactions in years 1 year   1 year              
Currency                    
Financial Instruments and Risk Management                    
Notional amount of contracts $ 3,222   $ 3,222              
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 $ 2   2              
Net gain (loss) included in AOCI, after-tax, expected to be recognized in net earnings within the next 12 months     $ 2              
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 $ (65)   $ (65)              
Longest duration of forecasted hedge transactions in years 3 years   3 years              
Equity contracts                    
Financial Instruments and Risk Management                    
Combined notional value, shares | shares 0.9   0.9              
Change in company's stock price (in dollars per share) | $ / shares     $ 1