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Earnings/(loss) per ordinary share - Summary of earnings (loss) per ordinary shares (Parenthetical) (Detail) - shares shares in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Earnings Per Share [Line Items] |  |  |
Weighted average number of shares outstanding | 1,786.7 | 1,797.3 | 1,824.7
Effect of dilutive securities shares | 12.8 | 11.3 |
Description of instruments with potential future dilutive effect not included in calculation of diluted earnings per share | This effect is calculated under the treasury stock method. In accordance with IAS 33 “Earnings per share”, for the purposes of calculating diluted loss per share, the effect of potentially dilutive securities has not been taken into account for the year ended 31 December 2015. |  |
Rio Tinto plc [member] |  |  |
Earnings Per Share [Line Items] |  |  |
Weighted average number of shares outstanding | 1,364.5 | 1,373.7 | 1,398.1
Rio Tinto Limited [member] |  |  |
Earnings Per Share [Line Items] |  |  |
Weighted average number of shares outstanding | 422.3 | 423.6 | 426.6

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- Definition The number of dilutive potential ordinary shares that relate to the assumed exercise of the entity's share options. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 33 -IssueDate 2016-01-13 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2016-03-30&anchor=para_70_b&doctype=Standard -URIDate 2016-03-31 + Details
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- Definition The description of instruments (including contingently issuable shares) that could potentially dilute basic earnings per share in the future, but were not included in the calculation of diluted earnings per share because they are antidilutive for the period(s) presented. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2016-01-13 -Paragraph 70 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2016-03-30&anchor=para_70_c&doctype=Standard -URIDate 2016-03-31 + Details
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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- Definition The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2016-01-13 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2016-03-30&anchor=para_70_b&doctype=Standard -URIDate 2016-03-31 + Details
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- Details
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- Details
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