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Share capital - Summary of share capital (Parenthetical) (Detail) - Rio Tinto plc [member] - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Classes Of Share Capital [Line Items]
Ordinary shares issued	26,241	33,210	21,709
Number of shares bought back	32,937,109	0	40,912,881
Treasury shares [Member]
Disclosure Of Classes Of Share Capital [Line Items]
Ordinary shares issued	147,126	743,380

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- Definition

The number of shares issued by the entity.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 106
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_106_d&doctype=Standard
-URIDate 2016-03-31

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Shares purchased and cancelled.

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