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Related undertakings - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2017
Disclosure Of Significant Investments In Subsidiaries [Abstract] |
Effective equity holding percentage | 50.00%

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- References No definition available. + Details
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Namespace Prefix: | ifrs-full_
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Balance Type: | na
Period Type: | duration

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- Definition Effective group ownership percentage. + References No definition available. + Details
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Namespace Prefix: | rio_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration