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Share Capital - Summary of Share Capital (Parenthetical) (Detail)
$ / shares in Units, $ in Millions
 1 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
Jun. 30, 2021
$ / shares
shares
Jun. 30, 2020
$ / shares
Jun. 30, 2019
USD ($)
$ / shares
Sep. 02, 2021
shares
Jun. 30, 2021
£ / shares
shares
Jun. 30, 2020
£ / shares
Jun. 30, 2019
£ / shares
Disclosure of classes of share capital [line items]                
Off-market buy-back program | $ $ 5,200     $ 5,220        
BHP Group Limited [member]                
Disclosure of classes of share capital [line items]                
Par value   $ 0.50            
BHP Group Limited [member] | Major ordinary share transactions [member]                
Disclosure of classes of share capital [line items]                
Number of ordinary shares issued on the exercise of awards | shares         4,400,000      
BHP Group Plc [member]                
Disclosure of classes of share capital [line items]                
Par value   0.50            
Special Voting share of US$0.50 par value [member] | BHP Group Plc [member]                
Disclosure of classes of share capital [line items]                
Par value   $ 0.50 $ 0.50 $ 0.50        
Number of ordinary shares issued on the exercise of awards | shares   1       1    
5.5% Preference shares [member]                
Disclosure of classes of share capital [line items]                
Par value | £ / shares           £ 1 £ 1 £ 1
Dividend rate percentage   5.50% 5.50% 5.50%        
5.5% Preference shares [member] | BHP Group Plc [member]                
Disclosure of classes of share capital [line items]                
Par value | £ / shares           £ 1 £ 1 £ 1
Dividend rate percentage   5.50% 5.50% 5.50%