XML 245 R178.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Share capital - Rio Tinto plc - Additional information (Detail) - USD ($)
$ in Millions
 12 Months Ended
Jan. 01, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
American depository receipts        
Disclosure of classes of share capital [line items]        
Value of shares purchased by employee share ownership trusts   $ 43 $ 140 $ 39
Rio Tinto plc [Member]        
Disclosure of classes of share capital [line items]        
Shares held in the employee share ownership trusts on behalf of Rio Tinto plc   821,589    
Number of shares bought back   28,356,034 63,984,287 (32,937,000)
Rio Tinto plc [Member] | Major ordinary share transactions [member]        
Disclosure of classes of share capital [line items]        
Number of shares bought back 3,233,874      
Rio Tinto plc [Member] | American depository receipts        
Disclosure of classes of share capital [line items]        
ADRs held by the Employee share ownership Trust (ESOT)   44,666