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Acquisition of Asanko Gold - Summary of Key Assumptions Used to Determine Fair Value of the Net Identifiable Assets Acquired (Detail) | 12 Months Ended
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Dec. 31, 2018 oz
Disclosure of detailed information about business combination [line items] |
Discount rate | 10.27%
Life-of-mine - 2019 to 2030 | 12 years
Within one year [member] | US Dollars [member] |
Disclosure of detailed information about business combination [line items] |
US$ gold price | 1,200
Later than one year [member] | US Dollars [member] |
Disclosure of detailed information about business combination [line items] |
US$ gold price | 1,300

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