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Rio Tinto financial information by business unit - Schedule of financial information by business unit (Parenthetical) (Detail) - USD ($)
$ in Millions
 1 Months Ended 6 Months Ended
Mar. 27, 2018
Mar. 22, 2018
Mar. 20, 2018
Sep. 01, 2017
May 31, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Disclosure Of Operating Segments [Line Items]                
Loss on other restructuring costs           $ 68    
Information System & Technology spend           $ 49    
Percentage of capital expenditure in subsidiaries           100.00%    
Reportable segments [Member]                
Disclosure Of Operating Segments [Line Items]                
Operating assets           $ 47,562   $ 48,556
Reportable segments [Member] | Energy & Minerals [Member]                
Disclosure Of Operating Segments [Line Items]                
Operating assets           $ 3,848   6,313
Hope Downs Joint Venture [member]                
Disclosure Of Operating Segments [Line Items]                
Proportion of ownership interest in joint venture           50.00%    
Robe river iron associates [member]                
Disclosure Of Operating Segments [Line Items]                
Proportion of ownership interest in joint venture           65.00%    
Proportion of net beneficial interest           53.00%    
Freeport Mc Mo Ran Inc [Member]                
Disclosure Of Operating Segments [Line Items]                
Percentage of material mined           40.00%    
Diavik joint venture [member]                
Disclosure Of Operating Segments [Line Items]                
Proportion of ownership interest in joint venture           60.00%    
Hail Creek Coal Mine [Member]                
Disclosure Of Operating Segments [Line Items]                
Proportion of ownership interest in joint venture           82.00%    
Hail Creek Coal Mine [Member] | 2018 Disposals [Member]                
Disclosure Of Operating Segments [Line Items]                
Ownership interest in joint venture disposed     82.00%          
Kestrel Underground Coal Mine [Member]                
Disclosure Of Operating Segments [Line Items]                
Proportion of ownership interest in joint venture           80.00%    
Kestrel Underground Coal Mine [Member] | 2018 Disposals [Member]                
Disclosure Of Operating Segments [Line Items]                
Proportion of ownership interest in joint venture 80.00%              
Receipts from non-refundable deposits           $ 338    
Hail Creek Coal Mine [Member]                
Disclosure Of Operating Segments [Line Items]                
Ownership interest in joint venture disposed     82.00%          
Valeria | Australia [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership interest in joint venture disposed     71.20%          
Proportion of ownership amount in joint venture disposed     $ 1,700          
Winchester South Member                
Disclosure Of Operating Segments [Line Items]                
Ownership interest in joint venture disposed   75.00%            
Winchester South Member | Australia [member]                
Disclosure Of Operating Segments [Line Items]                
Proportion of ownership amount in joint venture disposed   $ 200            
Kestrel [Member]                
Disclosure Of Operating Segments [Line Items]                
Ownership interest in joint venture disposed 80.00%              
Kestrel [Member] | Australia [member]                
Disclosure Of Operating Segments [Line Items]                
Proportion of ownership amount in joint venture disposed $ 2,250              
Hunter valley operations [member]                
Disclosure Of Operating Segments [Line Items]                
Proportion Of Voting Power Held In Subsidiary             67.60%  
Mount thorley co venture [member]                
Disclosure Of Operating Segments [Line Items]                
Proportion Of Voting Power Held In Subsidiary             80.00%  
Warkworth joint venture [member]                
Disclosure Of Operating Segments [Line Items]                
Proportion Of Voting Power Held In Subsidiary             55.60%  
30 Percent [Member] | Robe river iron associates [member]                
Disclosure Of Operating Segments [Line Items]                
Net beneficial interest held percentage           30.00%    
Net beneficial interest held percentage as owned subsidiary           60.00%    
35 Percent [Member] | Robe river iron associates [member]                
Disclosure Of Operating Segments [Line Items]                
Net beneficial interest held percentage           35.00%    
Net beneficial interest held percentage as owned subsidiary           100.00%    
Hamersley Iron Pty Limited [Member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           100.00%    
Oyu Tolgoi LLC [member] | Turquoise hill resources Ltd [member]                
Disclosure Of Operating Segments [Line Items]                
Percentage of share class held in subsidiaries           50.80%    
Oyu Tolgoi LLC [member] | Turquoise hill resources Ltd [member] | Oyo Tolgoi Copper-Gold Mine [Member]                
Disclosure Of Operating Segments [Line Items]                
Percentage of share class held in subsidiaries           66.00%    
Argyle Diamonds Limited [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           100.00%    
Coal & Allied Industries Limited [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary       100.00%     100.00%  
Proportion of ownership interest in subsidiaries disposed       100.00%        
Rio Tinto Coal Australia [Member] | Reportable segments [Member] | Energy & Minerals [Member]                
Disclosure Of Operating Segments [Line Items]                
Operating assets           $ (1,225)   $ 1,040
Rio Tinto Fer et Titane Inc. [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           100.00%    
QIT Madagascar Minerals SA [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           80.00%    
Richards Bay Minerals [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           74.00%    
Energy Resources of Australia Limited [Member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           68.40%    
Rossing Uranium Limited [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           68.60%    
Simfer Jersey Limited [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary         53.00% 53.00%    
Simfer S.A. [member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           85.00%    
Non-controlling interest (%), Subsidiary           45.05%    
Gove Alumina Refinery and Rio Tinto Marine [Member]                
Disclosure Of Operating Segments [Line Items]                
Ownership percentage in subsidiary           100.00%