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Share capital - Rio Tinto Limited - Summary of share capital (Detail)
$ in Millions, $ in Millions
 1 Months Ended 12 Months Ended
Nov. 30, 2017
shares
Apr. 30, 2015
shares
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2017
AUD ($)
shares
Dec. 31, 2016
USD ($)
shares
Dec. 31, 2016
AUD ($)
shares
Dec. 31, 2015
USD ($)
shares
Disclosure Of Classes Of Share Capital [Line Items]              
Adjustment on currency translation | $     $ 908        
Rio Tinto Limited [member]              
Disclosure Of Classes Of Share Capital [Line Items]              
Issued and fully paid up share capital at beginning balance     3,915 $ 4,004 $ 3,950   $ 4,535
Adjustment on currency translation | $     310   (35)   (503)
Ordinary shares purchased and cancelled | $     (85)       (82)
Issued and fully paid up share capital at ending balance     $ 4,140 $ 3,893 $ 3,915 $ 4,004 $ 3,950
Number of issued and fully paid up share capital at beginning balance | shares     424,190,000 424,190,000 424,190,000 424,190,000 435,760,000
Ordinary shares purchased and cancelled | shares (11,778,064) (11,566,308) (11,780,000) (11,780,000)     (11,570,000)
Number of issued and fully paid up share capital at ending balance | shares     412,410,000 412,410,000 424,190,000 424,190,000 424,190,000
Rio Tinto Limited [member] | Special voting share [member]              
Disclosure Of Classes Of Share Capital [Line Items]              
Other share classes     1 only 1 only 1 only 1 only 1 only
Rio Tinto Limited [member] | DLC dividend share [member]              
Disclosure Of Classes Of Share Capital [Line Items]              
Other share classes     1 only 1 only 1 only 1 only 1 only