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Principal subsidiaries - Summary of principal in subsidiaries (Parenthetical) (Detail) |  | 7 Months Ended | 12 Months Ended
--- | --- | --- | ---
Aug. 01, 2018 | Aug. 01, 2018 | Dec. 31, 2018
Oyu Tolgoi LLC [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Indirect interest in subsidiary |  |  | 33.50%
Robe river iron associates [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 65.00%
Non-controlling interest (%), Subsidiary |  |  | 12.00%
Proportion of net beneficial interest |  |  | 53.00%
Percentage of ownership interest exchanged in joint venture |  |  | 65.00%
Hail Creek [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Percentage of ownership interest exchanged in joint venture |  | 82.00% |
Hail Creek [Member] | 2018 Disposals [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership interest in joint venture disposed | 82.00% |  |
Kestrel Underground Coal Mine [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Percentage of ownership interest exchanged in joint venture |  | 80.00% |
Kestrel Underground Coal Mine [Member] | 2018 Disposals [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership interest in joint venture disposed | 80.00% |  |
Consorcio De Aluminio Do Maranhao [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Percentage of ownership interest exchanged in joint venture |  |  | 10.00%
Diavik Joint Venture [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Percentage of ownership interest exchanged in joint venture |  |  | 60.00%
Contractual obligations corresponding to receivable or contingent asset |  |  | 40.00%
Robe River Mining Co Pty Ltd [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 60.00%
Non-controlling interest (%), Subsidiary |  |  | 40.00%
Robe River Mining Co Pty Ltd [member] | Robe river iron associates [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Non-controlling interest (%), Subsidiary |  |  | 30.00%
North Mining Limited [member] | Ordinary shares [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 100.00%
North Mining Limited [member] | Robe river iron associates [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Non-controlling interest (%), Subsidiary |  |  | 35.00%
Queensland Coal Pty Limited [member] | Ordinary shares [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 100.00%
Queensland Coal Pty Limited [member] | Hail Creek [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Percentage of ownership interest exchanged in joint venture |  |  | 82.00%
Queensland Coal Pty Limited [member] | Kestrel Underground Coal Mine [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Percentage of ownership interest exchanged in joint venture |  |  | 80.00%
Simfer Jersey Limited [member] | Ordinary shares [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 53.00%
Non-controlling interest (%), Subsidiary |  |  | 47.00%
Simfer S.A. [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 85.00%
Non-controlling interest (%), Subsidiary |  |  | 45.05%
Indirect interest in subsidiary |  |  | 45.05%
QIT Madagascar Minerals SA [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 80.00%
Portion of additional economic interest held through non voting investment |  |  | 5.00%
Portion of economic interest held through non voting investment |  |  | 85.00%
Non-controlling interest voting rights |  |  | 20.00%
QIT Madagascar Minerals SA [member] | Common shares [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 80.00%
Proportion of class held (%), Subsidiary |  |  | 80.00%
QIT Madagascar Minerals SA [member] | Common Shares and Investment Certificates [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Non-controlling interest (%), Subsidiary |  |  | 15.00%
Turquoise Hill Resources Ltd [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 50.79%
Turquoise Hill Resources Ltd [member] | Oyu Tolgoi LLC [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 66.00%
Rossing Uranium [member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 68.60%
Proportion of class held (%), Subsidiary |  |  | 35.57%
Non-controlling interest voting rights |  |  | 64.43%
Richards Bay Mining (Proprietary) Limited [member] | B Ordinary, B Preference and Parent Preference Shares [Member] |  |  |
Disclosure Of Significant Investments In Subsidiaries [Line Items] |  |  |
Ownership percentage in subsidiary |  |  | 74.00%
Non-controlling interest (%), Subsidiary |  |  | 26.00%

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