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Significant Events - Additional Information (Detail)
 12 Months Ended
Aug. 08, 2018
Aug. 06, 2018
USD ($)
Jun. 30, 2018
USD ($)
Jun. 30, 2018
BRL (R$)
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Jun. 30, 2018
BRL (R$)
Jun. 29, 2018
USD ($)
Jun. 25, 2018
USD ($)
Jun. 25, 2018
BRL (R$)
Disclosure of significant events [Line items]                    
Funding provided during the period     $ 142,000,000              
Settlement claim     $ 3,503,000,000   $ 3,609,000,000          
Samarco dam failure [member]                    
Disclosure of significant events [Line items]                    
Percentage of charges recognised in Group's results     100.00% 100.00%            
Funding provided during the period     $ 80,000,000              
Additional share of losses     80,000,000   134,000,000 $ 655,000,000        
Provision before tax and after discounting in respect of its obligations under the Framework Agreement     1,285,000,000   1,057,000,000 1,200,000,000        
Provision paid     285,000,000   $ 308,000,000          
Samarco dam failure [member] | Dam Stabilisation and Expert Costs [member]                    
Disclosure of significant events [Line items]                    
Provision paid     4,000,000              
Samarco dam failure [member] | State Prosecutors in Minas Gerais [member]                    
Disclosure of significant events [Line items]                    
Settlement claim     2,000,000,000       R$ 7,500,000,000      
Samarco dam failure [member] | State Prosecutors in Esprito Santo [member]                    
Disclosure of significant events [Line items]                    
Settlement claim     520,000,000       2,000,000,000      
Samarco dam failure [member] | Public defenders in Minas Gerais [member]                    
Disclosure of significant events [Line items]                    
Settlement claim     2,600,000,000       10,000,000,000      
Samarco dam failure [member] | Preliminary Agreement [member] | Federal public prosecution office claim [member]                    
Disclosure of significant events [Line items]                    
Preliminary agreement suspended amount     $ 2,000,000,000 R$ 7,700,000,000            
Samarco dam failure [member] | Framework agreement [member]                    
Disclosure of significant events [Line items]                    
Term of agreement     15 years 15 years            
Samarco dam failure [member] | Governance Agreement [member] | Public civil claim [member]                    
Disclosure of significant events [Line items]                    
Settlement claim                 $ 5,200,000,000 R$ 20,000,000,000
Preliminary agreement suspended amount     $ 310,000,000 R$ 1,200,000,000            
Samarco dam failure [member] | Governance Agreement [member] | Federal public prosecution office claim [member]                    
Disclosure of significant events [Line items]                    
Settlement claim                 $ 40,000,000,000 R$ 155,000,000,000
Suspension period of claim 2 years                  
Settlement agreement [member] | United States class action complaint [member]                    
Disclosure of significant events [Line items]                    
In-principle settlement agreement amount   $ 50,000,000                
Samarco Mineracao S.A. [member]                    
Disclosure of significant events [Line items]                    
Percentage of interest in joint venture investment     50.00% 50.00% 50.00%          
Additional share of losses           $ 655,000,000        
Samarco Mineracao S.A. [member] | Framework agreement [member]                    
Disclosure of significant events [Line items]                    
Commitments     $ 1,878,000,000              
Samarco Mineracao S.A. [member] | Samarco dam failure [member]                    
Disclosure of significant events [Line items]                    
Provision paid     200,000,000   $ 300,000,000          
Commitments     1,100,000,000   1,500,000,000          
Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Brazilian Social Contribution Levy [Member]                    
Disclosure of significant events [Line items]                    
Settlement claim     1,400,000,000       5,400,000,000      
Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Brazilian corporate income tax rate [Member]                    
Disclosure of significant events [Line items]                    
Settlement claim     1,100,000,000       R$ 4,200,000,000      
Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Framework agreement [member]                    
Disclosure of significant events [Line items]                    
Provision before tax and after discounting in respect of its obligations under the Framework Agreement     2,600,000,000   2,100,000,000          
BHP Billiton Brasil Ltda [member] | Samarco dam failure [member] | Preliminary Agreement [member] | Insurance bonds [Member]                    
Disclosure of significant events [Line items]                    
Interim security amount preliminary agreement     335,000,000 R$ 1,300,000,000            
BHP Billiton Brasil Ltda [member] | Samarco dam failure [member] | Preliminary Agreement [member] | Liquid assets [Member]                    
Disclosure of significant events [Line items]                    
Interim security amount preliminary agreement     25,000,000 100,000,000            
BHP Billiton Brasil Ltda [member] | Samarco dam failure [member] | Preliminary Agreement [member] | Charge over assets [Member]                    
Disclosure of significant events [Line items]                    
Interim security amount preliminary agreement     210,000,000 800,000,000            
BHP Billiton Brasil Ltda [member] | Samarco dam failure [member] | Preliminary Agreement [member] | Allocated within next four years [Member]                    
Disclosure of significant events [Line items]                    
Interim security amount preliminary agreement     $ 50,000,000 R$ 200,000,000            
Allocation period     4 years 4 years            
BHP Billiton Brasil Ltda [member] | Samarco dam failure [member] | Framework agreement [member]                    
Disclosure of significant events [Line items]                    
Announced funding obligations under the Framework Agreement               $ 158,000,000    
Provision before tax and after discounting in respect of its obligations under the Framework Agreement     $ 1,300,000,000   $ 1,100,000,000          
Percentage of remaining costs expected to be incurred by December 2020     65.00% 65.00%            
BHP Billiton Brasil Ltda [member] | Samarco dam failure [member] | Governance Agreement [member]                    
Disclosure of significant events [Line items]                    
Term of agreement     30 months 30 months            
BHP Billiton Brasil Ltda [member] | Samarco dam failure [member] | Governance Agreement [member] | Top of range [Member]                    
Disclosure of significant events [Line items]                    
Interim security amount preliminary agreement     $ 570,000,000 R$ 2,200,000,000            
BHP Billiton Brasil Ltda [member] | Samarco Mineracao S.A. [member]                    
Disclosure of significant events [Line items]                    
Percentage of interest in joint venture investment     50.00% 50.00%            
Adjustment in joint venture investment                  
Funding provided during the period     80,000,000              
Additional share of losses     80,000,000              
Dividends received     0              
Profits available for distribution     0              
BHP Billiton Brasil Ltda [member] | Samarco Mineracao S.A. [member] | Samarco dam failure [member]                    
Disclosure of significant events [Line items]                    
Undrawn amount     16,000,000              
BHP Billiton Brasil Ltda [member] | Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Dam Stabilisation and Expert Costs [member]                    
Disclosure of significant events [Line items]                    
Provision paid     4,000,000              
BHP Billiton Brasil Ltda [member] | Samarco Mineracao S.A. [member] | Samarco dam failure [member] | Short-term facility [Member]                    
Disclosure of significant events [Line items]                    
Commitments     $ 53,000,000