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Share capital - Rio Tinto Limited - Summary of share capital (Detail) - USD ($)
$ in Millions
 1 Months Ended 12 Months Ended
Nov. 30, 2018
Nov. 30, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure Of Classes Of Share Capital [Line Items]          
Adjustment on currency translation     $ 386    
Rio Tinto Limited [member]          
Disclosure Of Classes Of Share Capital [Line Items]          
Issued and fully paid up share capital at beginning balance     4,140 $ 3,915 $ 3,950
Adjustment on currency translation     (382) 310 (35)
Ordinary shares purchased and cancelled     (281) (85)  
Issued and fully paid up share capital at ending balance     $ 3,477 $ 4,140 $ 3,915
Number of issued and fully paid up share capital at beginning balance     412,410,000 424,190,000 424,190,000
Ordinary shares purchased and cancelled (41,198,134) (11,778,064) (41,200,000) (11,780,000)  
Number of issued and fully paid up share capital at ending balance     371,210,000 412,410,000 424,190,000
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
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