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Financial instruments and risk management - Commodity price risk - Additional information (Detail) - Commodity price risk [Member] lb in Millions | 12 Months Ended
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Dec. 31, 2019 USD ($) lb | Dec. 31, 2018 USD ($) lb
Disclosure of detailed information about financial instruments [line items] |  |
Description of hedging strategy | Rio Tinto’s exposure to commodity prices is diversified by virtue of its broad commodity base and the Group does not generally consider that commodity fixed price hedging would provide a long-term benefit to shareholders. |
Copper [Member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Quantity of unsettled copper sales | lb | 220 | 240
Provisionally priced unsettled copper sales per pound | $ 0 | $ 277
Increase (Decrease) in net earnings due to price change | $ 38,000,000 | $ 37,000,000
Copper [Member] | Level 3 [Member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Percentage of increase in copper price | 10.00% |

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- Definition The description of hedging instruments used to hedge risk exposures and how they are used. [Refer: Hedging instruments [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph 22B -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_22B_a&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The increase (decrease) in contract assets resulting from cumulative catch-up adjustments to revenue arising from a change in an estimate of the transaction price. The transaction price is the amount of consideration to which an entity expects to be entitled in exchange for transferring promised goods or services to a customer, excluding amounts collected on behalf of third parties (for example, some sales taxes). [Refer: Increase (decrease) through cumulative catch-up adjustments to revenue, contract assets] + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Name IFRS -Number 15 -IssueDate 2019-01-01 -Paragraph 118 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=15&code=ifrs-tx-2019-en-r&anchor=para_118_b&doctype=Standard -URIDate 2019-03-27 + Details
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