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Share capital - Rio Tinto plc - Additional information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Classes Of Share Capital [Line Items]
ADRs held by the Employee share ownership Trust (ESOT)	0	0	0
Share of Rio Tinto plc and American depository receipts [member]
Disclosure Of Classes Of Share Capital [Line Items]
Value of shares purchased by employee share ownership trusts	$ 38.9	$ 40.1	$ 34.1
Rio Tinto plc [member]
Disclosure Of Classes Of Share Capital [Line Items]
Shares to held in the employee share ownership trusts on behalf of Rio Tinto plc	835,062
Rio Tinto plc [member] | American depository receipts [member]
Disclosure Of Classes Of Share Capital [Line Items]
ADRs held by the Employee share ownership Trust (ESOT)	38,849

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The number of shares in the entity held by the entity or by its subsidiaries or associates. [Refer: Associates [member]; Subsidiaries [member]]

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 79
-Subparagraph a
-Clause vi
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_79_a_vi&doctype=Standard
-URIDate 2016-03-31

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