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Financial instruments and risk management - Commodity price risk - Additional information (Detail) - Commodity price risk [Member] lb in Millions, $ in Millions | 12 Months Ended
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Dec. 31, 2018 USD ($) lb | Dec. 31, 2017 USD ($) lb
Disclosure Of 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 Financial Instruments [Line Items] |  |
Quantity of unsettled copper sales | lb | 240 | 250
Provisionally priced unsettled copper sales per pound | $ 277 | $ 304
Increase (Decrease) in net earnings due to price change | $ 37 | $ 41

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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 -Note Effective 2018-01-01 -Name IFRS -Number 7 -IssueDate 2017-01-01 -Paragraph 22B -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_22B_a&doctype=Standard -URIDate 2017-03-09 + Details
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- Details
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