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Notes to financial information by business unit (Detail) - USD ($)
$ in Millions
 6 Months Ended 7 Months Ended
Aug. 01, 2018
Jun. 30, 2019
Aug. 01, 2018
Dec. 31, 2018
Disclosure of operating segments [line items]        
Percentage of capital expenditure in subsidiaries (as a percent)   100.00%    
Reportable segments        
Disclosure of operating segments [line items]        
Operating Assets   $ 44,420   $ 43,431
Reportable segments | Energy & Minerals        
Disclosure of operating segments [line items]        
Operating Assets   $ 4,424   3,696
Hamersley Iron Pty Limited        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   100.00%    
Argyle Diamonds Limited        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   100.00%    
Rio Tinto Coal Australia | Reportable segments | Energy & Minerals        
Disclosure of operating segments [line items]        
Operating Assets   $ 0   (837)
Rio Tinto Fer et Titane Inc.        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   100.00%    
QIT Madagascar Minerals SA        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   80.00%    
Richards Bay Minerals        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   74.00%    
Energy Resources of Australia Limited        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   68.40%    
Rossing Uranium Limited        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   68.60%    
Simfer Jersey Limited        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   53.00%    
Simfer S.A.        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   85.00%    
Non-controlling interest (as a percent)   45.05%    
Gove Alumina Refinery and Rio Tinto Marine        
Disclosure of operating segments [line items]        
Rio Tinto interest (as a percent)   100.00%    
Hope Downs Joint Venture        
Disclosure of operating segments [line items]        
Proportion of ownership interest in joint venture (as a percent)   50.00%    
Robe river iron associates        
Disclosure of operating segments [line items]        
Proportion of ownership interest in joint venture (as a percent)   65.00%    
Proportion of net beneficial interest (as a percent)   53.00%    
Robe river iron associates | 30 Percent        
Disclosure of operating segments [line items]        
Net beneficial interest held percentage (as a percent)   30.00%    
Net beneficial interest held percentage as owned subsidiary (as a percent)   60.00%    
Robe river iron associates | 35 Percent        
Disclosure of operating segments [line items]        
Net beneficial interest held percentage (as a percent)   35.00%    
Net beneficial interest held percentage as owned subsidiary (as a percent)   100.00%    
Freeport Mc Mo Ran Inc        
Disclosure of operating segments [line items]        
Percentage of material mined (as a percent)   40.00%    
Diavik joint venture        
Disclosure of operating segments [line items]        
Proportion of ownership interest in joint venture (as a percent)   60.00%    
Hail Creek Coal Mine        
Disclosure of operating segments [line items]        
Ownership interest in joint venture disposed (as a percent)     82.00%  
Hail Creek Coal Mine        
Disclosure of operating segments [line items]        
Ownership interest in joint venture disposed (as a percent) 82.00%      
Valeria        
Disclosure of operating segments [line items]        
Ownership interest in joint venture disposed (as a percent) 71.20%      
Turquoise hill resources Ltd | Oyu Tolgoi LLC        
Disclosure of operating segments [line items]        
Percentage of share class held in subsidiaries (as a percent)   50.80%    
Oyo Tolgoi Copper-Gold Mine | Turquoise hill resources Ltd | Oyu Tolgoi LLC        
Disclosure of operating segments [line items]        
Percentage of share class held in subsidiaries (as a percent)   66.00%    
Australia        
Disclosure of operating segments [line items]        
Operating Assets       $ (837)
Australia | Valeria        
Disclosure of operating segments [line items]        
Proportion of ownership amount in joint venture disposed $ 1,700      
Australia | Kestrel        
Disclosure of operating segments [line items]        
Proportion of ownership amount in joint venture disposed $ 2,250      
2018 Disposals | Kestrel Underground Coal Mine        
Disclosure of operating segments [line items]        
Ownership interest in joint venture disposed (as a percent)     80.00%