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Principal joint operations - Summary of principle joint operations (Parenthetical) (Detail) | 12 Months Ended
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Dec. 31, 2017 Subsidiary
Kestrel [member] |
Disclosure Of Joint Operations [Line Items] |
Group interest (%), Joint Operation | 80.00%
Principal activities, Joint Operation | Coal mining
New Zealand Aluminium Smelters Limited [member] |
Disclosure Of Joint Operations [Line Items] |
Group interest (%), Joint Operation | 79.36%
Principal activities, Joint Operation | Aluminium smelting
Queensland Alumina Limited [member] |
Disclosure Of Joint Operations [Line Items] |
Group interest (%), Joint Operation | 80.00%
Principal activities, Joint Operation | Alumina production
Pilbara Iron arrangement [Member] |
Disclosure Of Joint Operations [Line Items] |
Number of subsidiary | 2
Company of operation, Subsidiary | Pilbara Iron (Company) Services Pty Ltd and Pilbara Iron Pty Ltd.
Principal activities, Joint Operation | Infrastructure, corporate and mining services
Grasberg expansion [member] |
Disclosure Of Joint Operations [Line Items] |
Group interest (%), Joint Operation | 40.00%
Principal activities, Joint Operation | Copper and gold mining
Grasberg expansion [member] | Pre 2021 [Member] |
Disclosure Of Joint Operations [Line Items] |
Percentage of production limit under participation agreement | 40.00%
Grasberg expansion [member] | More than 5 years [member] |
Disclosure Of Joint Operations [Line Items] |
Percentage of production limit under participation agreement | 40.00%
Pechiney Reynolds Quebec Inc [member] |
Disclosure Of Joint Operations [Line Items] |
Group interest (%), Joint Operation | 50.20%
Principal activities, Joint Operation | Aluminium smelting
Pechiney Reynolds Quebec Inc [member] | Aluminerie De Becancour Inc [member] |
Disclosure Of Joint Operations [Line Items] |
Group interest (%), Joint Venture | 50.10%
Company of operation | Aluminerie de Bécancour, Inc.
Principal activities, Joint Operation | Aluminium smelter
Country of incorporation, Joint Venture | Canada

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