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Share Capital - Summary of Share Capital (Parenthetical) (Detail)
$ / shares in Units, $ in Millions
 1 Months Ended 2 Months Ended 12 Months Ended
Dec. 31, 2018
USD ($)
Sep. 05, 2019
shares
Jun. 30, 2019
USD ($)
$ / shares
shares
Jun. 30, 2018
$ / shares
shares
Jun. 30, 2017
$ / shares
shares
Jun. 30, 2019
£ / shares
Jun. 30, 2018
£ / shares
Jun. 30, 2017
£ / 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 | $ / shares     $ 0.50          
Number of ordinary shares issued on the exercise of awards     5,902,588 7,339,522 6,945,570      
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   0            
BHP Group Plc [member]                
Disclosure of classes of share capital [line items]                
Par value | $ / shares     $ 0.50          
Number of ordinary shares issued on the exercise of awards     275,984 711,705 940,070      
BHP Group Plc [member] | Major ordinary share transactions [member]                
Disclosure of classes of share capital [line items]                
Number of ordinary shares issued on the exercise of awards   0            
Special Voting share of US$0.50 par value [member] | BHP Group Plc [member]                
Disclosure of classes of share capital [line items]                
Par value | $ / shares     $ 0.5 $ 0.5 $ 0.5      
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%