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Impairment charges - Narrative (Details) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2023
Jun. 30, 2022
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]    
Impairment charges   $ 0
Property, plant and equipment    
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]    
Impairment charges $ 1,175 0
Alumina refineries | Aluminium    
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]    
Discount rate applied to cash flow projections 6.60%  
Impairment charges $ 1,175 $ 0
Impairment charges, net $ 828  
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 charges $ 948  
Queensland Alumina Limited (QAL) | Aluminium    
Disclosure of impairment loss recognised or reversed for cash-generating unit [line items]    
Impairment 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 charges $ 227