v3.26.1
Financial Instruments and Risk Management - General (Details)
$ / shares in Units, € in Millions, shares in Millions, $ in Millions
 3 Months Ended
Mar. 31, 2026
USD ($)
shares
approach
$ / shares
Mar. 31, 2025
USD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2025
EUR (€)
May 31, 2025
EUR (€)
Dec. 31, 2024
USD ($)
Financial Instruments and Risk Management            
Other comprehensive earnings (loss), net of tax $ 3 $ 61        
Total shareholders' equity 5,619 5,569 $ 5,421     $ 5,930
Accumulated Other Comprehensive Earnings (Loss)            
Financial Instruments and Risk Management            
Other comprehensive earnings (loss), net of tax 3 61        
Total shareholders' equity (866) $ (942) (869)     $ (1,003)
Accumulated Other Comprehensive Earnings (Loss) For Non Derivative Financial Instrument            
Financial Instruments and Risk Management            
Total shareholders' equity $ (505)   $ (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%    
Net Investment | Accumulated Other Comprehensive Earnings (Loss) For Non Derivative Financial Instrument            
Financial Instruments and Risk Management            
Other comprehensive earnings (loss), net of tax $ 20          
Total shareholders' equity $ 12          
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          
Notional amount of contracts $ 1,720          
Net gain (loss) included in AOCI, after-tax 44          
Net gain (loss) included in AOCI, after-tax, expected to be recognized in net earnings within the next 12 months $ 41          
Longest duration of forecasted hedge transactions in years 2 years          
Currency            
Financial Instruments and Risk Management            
Notional amount of contracts $ 3,375          
Net gain (loss) included in AOCI, after-tax 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          
Interest Rate            
Financial Instruments and Risk Management            
Notional amount of contracts $ 600          
Net gain (loss) included in AOCI, after-tax 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          
Net Investment            
Financial Instruments and Risk Management            
Notional amount of contracts $ 1,050          
Net gain (loss) included in AOCI, after-tax $ (63)          
Longest duration of forecasted hedge transactions in years 3 years          
Equity contracts            
Financial Instruments and Risk Management            
Combined notional value, shares | shares 0.9          
Change in company's stock price (in dollars per share) | $ / shares $ 1