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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
	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

X

- 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
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-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

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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

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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.

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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
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-Paragraph 70
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-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

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