Significant Events - Additional Information (Detail)
R$ in Millions, $ in Millions
 6 Months Ended 12 Months Ended
Aug. 08, 2018
USD ($)
Jun. 30, 2020
USD ($)
Jun. 30, 2021
USD ($)
Jun. 30, 2020
USD ($)
Jun. 30, 2019
USD ($)
Jun. 30, 2021
BRL (R$)
Dec. 31, 2019
USD ($)
Nov. 30, 2019
USD ($)
Aug. 08, 2018
BRL (R$)
Disclosure of significant events [line items]                  
Funding provided during the period     $ 219            
Impairment losses     2,635 $ 494 $ 264        
Settlement claim   $ 2,848 3,147 2,848          
Income recognised from insurance settlements     $ 573            
Termination of criminal charges against affected individuals by the federal court     8            
Appeal against termination of criminal charges still pending in federal court     7            
Samarco dam failure [member]                  
Disclosure of significant events [line items]                  
Percentage of charges recognised in Group's results     100.00%            
Impairment losses     $ 111 95 96        
Provision in addition to obligations under the Framework Agreement   2,051 2,792 2,051 $ 1,914        
Samarco dam failure [member] | State Prosecutors in Minas Gerais [member]                  
Disclosure of significant events [line items]                  
Settlement claim     1,500     R$ 7,500.0      
Samarco dam failure [member] | State Prosecutors in Esprito Santo [member]                  
Disclosure of significant events [line items]                  
Settlement claim     $ 400     2,000.0      
Samarco dam failure [member] | Public defenders in Minas Gerais [member]                  
Disclosure of significant events [line items]                  
Settlement claim   2,000   $ 2,000   10,000.0      
Samarco dam failure [member] | Framework agreement [member]                  
Disclosure of significant events [line items]                  
Term of agreement     15 years            
Term of agreement renewable     1 year            
Samarco dam failure [member] | Governance Agreement [member] | Federal public prosecution office claim [member]                  
Disclosure of significant events [line items]                  
Term of agreement 2 years                
Settlement claim     $ 30,000     155,000.0      
Preliminary agreement suspended amount $ 1,500               R$ 7,700.0
Samarco dam failure [member] | Governance Agreement [member] | Federal public prosecution office claim [member] | Definitive And Substantive Settlement Obligation Member [Member]                  
Disclosure of significant events [line items]                  
Settlement claim     $ 30,000     155,000.0      
Samarco Mineracao S.A. [member]                  
Disclosure of significant events [line items]                  
Percentage of interest in joint venture investment     50.00% 50.00%          
Samarco Mineracao S.A. [member] | Samarco dam failure [member]                  
Disclosure of significant events [line items]                  
Commitments   400 $ 700 $ 400          
Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Brazilian Social Contribution Levy [Member]                  
Disclosure of significant events [line items]                  
Settlement claim   1,200 1,200 1,200   5,900.0      
Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Brazilian Corporate Income Tax Rate [Member]                  
Disclosure of significant events [line items]                  
Settlement claim   900 900 900   4,600.0      
Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Framework agreement [member]                  
Disclosure of significant events [line items]                  
Provision in addition to obligations under the Framework Agreement   200 200 200          
BHP Brasil Ltda [member] | Samarco Germano dam decommissioning [member]                  
Disclosure of significant events [line items]                  
Provision     $ 232 227          
Percentage of decommissioning cost     50.00%            
BHP Brasil Ltda [member] | Framework agreement [member] | Insurance bonds [member]                  
Disclosure of significant events [line items]                  
Interim security amount preliminary agreement     $ 260     1.3      
BHP Brasil Ltda [member] | Samarco dam failure [member]                  
Disclosure of significant events [line items]                  
Funding provided during the period     111            
Impairment losses     111            
BHP Brasil Ltda [member] | Samarco dam failure [member] | Framework agreement [member]                  
Disclosure of significant events [line items]                  
Provision in addition to obligations under the Framework Agreement   1,800 $ 2,600 1,800          
Percentage of remaining costs expected to be incurred by December 2021     85.00%            
BHP Brasil Ltda [member] | Samarco dam failure [member] | Framework agreement [member] | Insurance bonds [member]                  
Disclosure of significant events [line items]                  
Interim security amount preliminary agreement     $ 440     2,200.0      
BHP Brasil Ltda [member] | Samarco dam failure [member] | Framework agreement [member] | Charge over assets [member]                  
Disclosure of significant events [line items]                  
Interim security amount preliminary agreement     160     800.0      
BHP Brasil Ltda [member] | Samarco dam failure [member] | Framework agreement [member] | Liquid assets [member]                  
Disclosure of significant events [line items]                  
Interim security amount preliminary agreement     20     R$ 100.0      
BHP Brasil Ltda [member] | Samarco Mineracao S.A. [member]                  
Disclosure of significant events [line items]                  
Investment in Samarco     0            
Dividends received     0            
Profits available for distribution     $ 0            
Percentage of interest in joint venture investment     50.00%            
Commitments   200 $ 350 $ 200          
Payment of approved amount to jointventure   $ 40              
BHP Brasil Ltda [member] | Samarco Mineracao S.A. [member] | Samarco dam failure [member]                  
Disclosure of significant events [line items]                  
Commitments amount               $ 765  
BHP Brasil Ltda [member] | Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Dam Stabilisation And Expert Costs [Member]                  
Disclosure of significant events [line items]                  
Commitments amount             $ 725