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Share-based payments -Management Share Plans, Bonus Deferral Plans, Global Employee Share Plans and UK Share Plan (combined) (Detail)
 12 Months Ended
Dec. 31, 2017
GBP (£)
Dec. 31, 2017
AUD ($)
Dec. 31, 2016
GBP (£)
Dec. 31, 2016
AUD ($)
Dec. 31, 2017
AUD ($)
Dec. 31, 2016
AUD ($)
Dec. 31, 2015
GBP (£)
Dec. 31, 2015
AUD ($)
Share Incentive Plans | Rio Tinto plc [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 3,473,092   3,305,966   3,473,092 3,305,966 3,211,727 3,211,727
Number of non-vested shares, awarded 1,499,374 1,499,374 1,673,017 1,673,017        
Number of non-vested shares, forfeited 159,669 159,669 246,806 246,806        
Number of non-vested shares, Cancelled (51,773) (51,773)            
Number of non-vested shares, vested 1,120,806 1,120,806 1,331,972 1,331,972        
Weighted average fair value at grant date, non-vested shares at beginning balance £ 27.23   £ 26.00       £ 29.70  
Weighted average fair value at grant date, non-vested shares, awarded 32.50   20.62          
Weighted average fair value at grant date, non-vested shares, forfeited 29.46   23.02          
Weighted average fair value at grant date, non-vested shares, cancelled 25.82              
Weighted average fair value at grant date, non-vested shares, vested £ 30.41   £ 28.72          
Share Incentive Plans | Rio Tinto Limited [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 2,933,237   2,986,080   2,933,237 2,986,080 2,993,396 2,993,396
Number of non-vested shares, awarded 1,156,078 1,156,078 1,405,348 1,405,348        
Number of non-vested shares, forfeited 127,905 127,905 164,020 164,020        
Number of non-vested shares, Cancelled (95,203) (95,203)            
Number of non-vested shares, vested 985,813 985,813 1,248,644 1,248,644        
Weighted average fair value at grant date, non-vested shares at beginning balance | $         $ 54.15 $ 53.32   $ 58.09
Weighted average fair value at grant date, non-vested shares, awarded | $   $ 61.05   $ 45.27        
Weighted average fair value at grant date, non-vested shares, forfeited | $   53.61   $ 54.48        
Weighted average fair value at grant date, non-vested shares, cancelled | $   $ 51.18            
Weighted average fair value at grant date, non-vested shares, vested | $         $ 60.06 $ 55.54    
Management share plans [member] | Rio Tinto plc [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 1,897,318   1,668,590   1,897,318 1,668,590    
Weighted average fair value at grant date, non-vested shares at beginning balance £ 27.99   £ 25.79          
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 653,776 653,776 758,776 758,776        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) £ 35.33   £ 20.07          
Management share plans [member] | Rio Tinto Limited [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 1,617,838   1,530,814   1,617,838 1,530,814    
Weighted average fair value at grant date, non-vested shares at beginning balance | $         $ 55.42 $ 53.88    
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 577,083 577,083 701,965 701,965        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $   $ 67.93   $ 43.93        
Bonus deferral plans [member] | Rio Tinto plc [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 281,994   312,767   281,994 312,767    
Weighted average fair value at grant date, non-vested shares at beginning balance £ 25.53   £ 23.24          
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 170,036 170,036 112,623 112,623        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) £ 34.44   £ 30.36          
Bonus deferral plans [member] | Rio Tinto Limited [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 153,966   148,158   153,966 148,158    
Weighted average fair value at grant date, non-vested shares at beginning balance | $         $ 52.83 $ 50.25    
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 88,644 88,644 113,407 113,407        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $   $ 69.98   $ 56.78        
Global employee share plans [member] | Rio Tinto plc [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 1,196,937   1,223,144   1,196,937 1,223,144    
Weighted average fair value at grant date, non-vested shares at beginning balance £ 26.42   £ 26.90          
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 382,585 382,585 344,072 344,072        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) £ 33.56   £ 24.33          
Global employee share plans [member] | Rio Tinto Limited [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 1,161,433   1,307,108   1,161,433 1,307,108    
Weighted average fair value at grant date, non-vested shares at beginning balance | $         $ 52.54 $ 53.03    
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 466,308 466,308 332,010 332,010        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $   $ 65.10   $ 48.69        
UK share plan [member] | Rio Tinto plc [member]                
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Line Items]                
Number of non-vested shares at beginning balance 96,843   101,465   96,843 101,465    
Weighted average fair value at grant date, non-vested shares at beginning balance £ 27.14   £ 27.00          
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 11,120 11,120 21,082 21,082        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) £ 34.56   £ 21.92