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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, 2018
AUD ($)
Dec. 31, 2018
GBP (£)
Dec. 31, 2017
AUD ($)
Dec. 31, 2017
GBP (£)
Dec. 31, 2018
GBP (£)
Dec. 31, 2017
GBP (£)
Dec. 31, 2016
AUD ($)
Dec. 31, 2016
GBP (£)
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 3,042,020   3,473,092   3,042,020 3,473,092 3,305,966 3,305,966
Number of non-vested shares, awarded 1,135,103 1,135,103 1,499,374 1,499,374        
Number of non-vested shares, forfeited 250,853 250,853 159,669 159,669        
Number of non-vested shares, Cancelled (33,563) (33,563) (51,773) (51,773)        
Number of non-vested shares, vested 1,281,759 1,281,759 1,120,806 1,120,806        
Weighted average fair value at grant date, non-vested shares at beginning balance         £ 31.43 £ 27.23   £ 26.00
Weighted average fair value at grant date, non-vested shares, awarded   £ 39.49   £ 32.50        
Weighted average fair value at grant date, non-vested shares, forfeited   30.26   29.46        
Weighted average fair value at grant date, non-vested shares, cancelled   26.52   25.82        
Weighted average fair value at grant date, non-vested shares, vested   £ 27.54   £ 30.41        
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 2,613,930   2,933,237   2,613,930 2,933,237 2,986,080 2,986,080
Number of non-vested shares, awarded 943,315 943,315 1,156,078 1,156,078        
Number of non-vested shares, forfeited 185,062 185,062 127,905 127,905        
Number of non-vested shares, Cancelled (36,613) (36,613) (95,203) (95,203)        
Number of non-vested shares, vested 1,040,947 1,040,947 985,813 985,813        
Weighted average fair value at grant date, non-vested shares at beginning balance | $ $ 61.71   $ 54.15       $ 53.32  
Weighted average fair value at grant date, non-vested shares, awarded | $ 78.36   61.05          
Weighted average fair value at grant date, non-vested shares, forfeited | $ 64.60   53.61          
Weighted average fair value at grant date, non-vested shares, cancelled | $ 52.84   51.18          
Weighted average fair value at grant date, non-vested shares, vested | $ $ 55.30   $ 60.06          
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 1,666,082   1,897,318   1,666,082 1,897,318    
Weighted average fair value at grant date, non-vested shares at beginning balance         £ 32.52 £ 27.99    
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 669,678 669,678 653,776 653,776        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting)   £ 40.03   £ 35.33        
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 1,520,292   1,617,838   1,520,292 1,617,838    
Weighted average fair value at grant date, non-vested shares at beginning balance | $ $ 64.06   $ 55.42          
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 570,173 570,173 577,083 577,083        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $ $ 80.87   $ 67.93          
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 203,900   281,994   203,900 281,994    
Weighted average fair value at grant date, non-vested shares at beginning balance         £ 37.86 £ 25.53    
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 221,198 221,198 170,036 170,036        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting)   £ 37.69   £ 34.44        
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 127,423   153,966   127,423 153,966    
Weighted average fair value at grant date, non-vested shares at beginning balance | $ $ 71.93   $ 52.83          
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 108,001 108,001 88,644 88,644        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $ $ 75.36   $ 69.98          
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 1,102,322   1,196,937   1,102,322 1,196,937    
Weighted average fair value at grant date, non-vested shares at beginning balance         £ 28.68 £ 26.42    
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 451,710 451,710 382,585 382,585        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting)   £ 39.06   £ 33.56        
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 966,215   1,161,433   966,215 1,161,433    
Weighted average fair value at grant date, non-vested shares at beginning balance | $ $ 56.66   $ 52.54          
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 473,420 473,420 466,308 466,308        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting) | $ $ 78.78   $ 65.10          
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 69,716   96,843   69,716 96,843    
Weighted average fair value at grant date, non-vested shares at beginning balance         £ 29.90 £ 27.14    
Number of vested awards settled in shares during the year (including dividend shares applied on vesting) 16,968 16,968 11,120 11,120        
Weighted average share price, Vested awards settled in shares during the year (including dividend shares applied on vesting)   £ 38.21   £ 34.56