XML 190 R183.htm IDEA: XBRL DOCUMENT v3.8.0.1
Share capital - Rio Tinto Limited - Summary of share capital (Parenthetical) (Detail) - Rio Tinto Limited [member] - $ / shares
 1 Months Ended 12 Months Ended
Nov. 30, 2017
Apr. 30, 2015
Dec. 31, 2017
Dec. 31, 2015
Disclosure Of Classes Of Share Capital [Line Items]        
Ordinary shares purchased and cancelled 11,778,064 11,566,308 11,780,000 11,570,000
Price per purchased share $ 63.67 $ 48.44    
Top of range [Member]        
Disclosure Of Classes Of Share Capital [Line Items]        
Number of shares bought back 42,400,000 43,500,000