v3.26.1
Investment in and Advances to Non-Consolidated Affiliates and Related Party Transactions - Additional Information (Details) - USD ($)
3 Months Ended 12 Months Ended
Feb. 18, 2026
Dec. 23, 2025
Mar. 31, 2024
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Schedule of Equity Method Investments [Line Items]            
Net sales       $ 18,434,000,000 $ 17,149,000,000 $ 16,210,000,000
Return of capital to our common shareholder     $ 100,000,000 35,000,000 0 $ 100,000,000
AV Minerals (Netherlands) N.V.            
Schedule of Equity Method Investments [Line Items]            
Stock issued during period (in shares) 1,333,333 5,000,000        
Sale of stock, number of shares issued (in shares) 1,333,333 5,000,000        
Sale of stock, consideration received $ 200,000,000 $ 750,000,000        
Sale of stock, price per share (in dollars per share) $ 150 $ 150        
Parent Company            
Schedule of Equity Method Investments [Line Items]            
Net sales       1,000,000 1,000,000  
Accounts receivable, net       $ 1,000,000    
Alunorf            
Schedule of Equity Method Investments [Line Items]            
Ownership percentage       50.00%    
Difference between carrying amount and underlying equity       $ 419,000,000    
Ulsan Aluminum, Ltd.            
Schedule of Equity Method Investments [Line Items]            
Ownership percentage       50.00%    
Contributions to equity method investee       $ 7,000,000 $ 21,000,000  
Difference between carrying amount and underlying equity       $ 42,000,000    
AluInfra Services SA            
Schedule of Equity Method Investments [Line Items]            
Ownership percentage       50.00%