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Impairment - Narrative (Details)
$ in Millions
 6 Months Ended
May 30, 2024
MW
Jun. 30, 2024
USD ($)
Jun. 30, 2023
USD ($)
Dec. 31, 2023
USD ($)
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Power arrangement, term of agreement 20 years      
Power arrangement, amount of power with set pricing (in megawatts) | MW 572      
Impairment (reversal) charge   $ (18) $ 1,175  
Deferred tax assets   3,435   $ 3,624
Impairment charges, net   (55) 828  
Impairment (reversals net of charges)/charges   (41) 1,175  
Impairment Charge (Reversal)        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Deferred tax assets   37    
Porto Trombetas (MRN)        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment (reversal) charge   35    
Impairment charges, net   23    
Property, plant and equipment        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment (reversal) charge   (41) 1,175  
Tiwai Point | Aluminium        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment (reversal) charge   (41) 0  
Impairment charges, net   (78)    
Alumina refineries | Aluminium        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment (reversal) charge   0 1,175  
Impairment charges, net   $ 0 $ 828  
Discount rate applied to cash flow projections     6.60%  
Impairment (reversals net of charges)/charges     $ 1,175  
Reduction in carbon emissions     0.50  
Increase in carbon tax     0.10  
Yarwun Alumina Refinery | Aluminium | Property, plant and equipment        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment (reversals net of charges)/charges     $ 948  
Queensland Alumina Limited (QAL) | Aluminium        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment (reversals net of charges)/charges     99  
Recoverable amount of asset     325  
Expected post-tax impairment charge if project not approved     325  
Queensland Alumina Limited (QAL) | Aluminium | Property, plant and equipment        
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]        
Impairment (reversals net of charges)/charges     $ 227