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Investments - Investments in Group companies (Detail) - Rio Tinto plc [member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Investments In Subsidiaries Joint Ventures And Associates [Abstract]
Investments in Group companies, beginning balance	$ 36,050	$ 36,180
Additions	45	58
Disposals		(160)
Other adjustments	(2)	(28)
Investments in Group companies, ending balance	$ 36,093	$ 36,050

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- Definition

The amount of investments in subsidiaries, joint ventures and associates in an entity's separate financial statements. [Refer: Associates [member]; Joint ventures [member]; Subsidiaries [member]; Investments in subsidiaries]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_55&doctype=Standard
-URIDate 2016-03-31

+ Details

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- Definition

Additions to investments in subsidiaries joint ventures and associates.

+ References

No definition available.

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- Definition

Disclosure of investments in subsidiaries joint ventures and associates.

+ References

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- Definition

Disposals from investments in subsidiaries joint ventures and associates.

+ References

No definition available.

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- Definition

Other adjustments to investments in subsidiaries joint ventures and associates.

+ References

No definition available.

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