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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 |  |

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