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Operating segments - Summary of underlying earnings within the reportable segments (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Disclosure of operating segments [Line Items]      
Underlying earnings $ 8,627 $ 5,100 $ 4,540
– attributable to owners of Rio Tinto (net earnings/(loss)) 8,762 4,617 (866)
Items excluded from underlying earnings 135 (483) (5,406)
Reportable segments [Member]      
Disclosure of operating segments [Line Items]      
Underlying earnings 9,642 6,064 5,515
Reportable segments [Member] | Iron Ore [Member]      
Disclosure of operating segments [Line Items]      
Underlying earnings 6,692 4,611 3,940
Reportable segments [Member] | Aluminium [Member]      
Disclosure of operating segments [Line Items]      
Underlying earnings 1,583 947 1,118
Reportable segments [Member] | Copper & Diamonds [member]      
Disclosure of operating segments [Line Items]      
Underlying earnings 263 (18) 370
Reportable segments [Member] | Energy & Minerals [Member]      
Disclosure of operating segments [Line Items]      
Underlying earnings 1,242 612 177
Reportable segments [Member] | Other operations [Member]      
Disclosure of operating segments [Line Items]      
Underlying earnings (138) (88) (90)
Other items [Member]      
Disclosure of operating segments [Line Items]      
– attributable to owners of Rio Tinto (net earnings/(loss)) (483) (241) (375)
Exploration and evaluation not attributed to product groups [Member]      
Disclosure of operating segments [Line Items]      
– attributable to owners of Rio Tinto (net earnings/(loss)) (178) (147) (211)
Finance costs [Member]      
Disclosure of operating segments [Line Items]      
– attributable to owners of Rio Tinto (net earnings/(loss)) $ (354) $ (576) $ (389)