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Earnings per ordinary share - Summary of earnings (loss) per ordinary shares (Parenthetical) (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Line Items]
Weighted average number of shares outstanding	1,719.3	1,786.7	1,797.3
Effect of dilutive securities shares	12.4	12.8	11.3
Rio Tinto plc [member]
Earnings Per Share [Line Items]
Weighted average number of shares outstanding	1,312.7	1,364.5	1,373.7
Rio Tinto Limited [member]
Earnings Per Share [Line Items]
Weighted average number of shares outstanding	406.6	422.3	423.6

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
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-IssueDate 2017-01-01
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-URIDate 2017-03-09

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X

- 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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X

- 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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-Number 33
-IssueDate 2017-01-01
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-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2017-03-01&anchor=para_70_b&doctype=Standard
-URIDate 2017-03-09

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