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Intangible assets - Summary of exploration and evaluation expenditure (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Exploration And Evaluation Expenditure [Abstract] |  |  |
Net expenditure in the year (net of proceeds of US$3 million (2016: US$208 million; 2015: US$nil) on disposal of undeveloped projects) | $ (493) | $ (284) | $ (705)
Non-cash movements and non-cash proceeds on disposal of undeveloped projects | (24) | (177) | (15)
Amount capitalised during the year | 57 | 8 | 152
Net charge for the year | (460) | (453) | (568)
Reconciliation to income statement |  |  |
Exploration and evaluation costs | (445) | (497) | (576)
Profit relating to interests in undeveloped projects | (15) | 44 | 8
Net charge for the year | $ (460) | $ (453) | $ (568)

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- Definition The amount of expense arising from the search for mineral resources, including minerals, oil, natural gas and similar non-regenerative resources after the entity has obtained legal rights to explore in a specific area, as well as the determination of the technical feasibility and commercial viability of extracting the mineral resource. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 6 -IssueDate 2016-01-13 -Paragraph 24 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=6&date=2016-03-30&anchor=para_24_b&doctype=Standard -URIDate 2016-03-31 + Details
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Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition The amount of liabilities arising from the search for mineral resources, including minerals, oil, natural gas and similar non-regenerative resources after the entity has obtained legal rights to explore in a specific area, as well as the determination of the technical feasibility and commercial viability of extracting the mineral resource. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 6 -IssueDate 2016-01-13 -Paragraph 24 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=6&date=2016-03-30&anchor=para_24_b&doctype=Standard -URIDate 2016-03-31 + Details
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Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition The net outflow (cash and non-cash) for the purchase of exploration and evaluation assets. + References No definition available. + Details
Name: | rio_ExplorationAndEvaluationCharge
Namespace Prefix: | rio_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition The net cash outflow for the purchase of exploration and evaluation assets. + References No definition available. + Details
Name: | rio_ExplorationAndEvaluationExpenditure
Namespace Prefix: | rio_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Exploration and evaluation expenditure [abstract] + References No definition available. + Details
Name: | rio_ExplorationAndEvaluationExpenditureAbstract
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- Definition Non-cash movements and non-cash proceeds on disposal of undeveloped projects. + References No definition available. + Details
Name: | rio_NoncashMovementsAndProceedsOnDisposalOfUndevelopedProjects
Namespace Prefix: | rio_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition The amount of Profit/(loss) relating to interests in undeveloped projects. + References No definition available. + Details
Name: | rio_ProfitLossRelatingToInterestsInUndevelopedProjects
Namespace Prefix: | rio_
Data Type: | xbrli:monetaryItemType
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- Definition Reconciliation to income statement. + References No definition available. + Details
Name: | rio_ReconciliationToIncomeStatementAbstract
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Balance Type: | na
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