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DERIVATIVE INSTRUMENTS - Additional information (Details) $ in Millions | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2018 lb oz $ / oz | Dec. 31, 2019 item t | Dec. 31, 2019 lb | Dec. 31, 2019 oz | Dec. 31, 2019 USD ($)
Disclosure of derivative instruments |  |  |  |  |
Strike price of put options at the time of purchasing | $ / oz | 1,230 |  |  |  |
Strike price of call options at the time of selling | $ / oz | 1,300 |  |  |  |
Foreign exchange forward contracts |  |  |  |  |
Disclosure of derivative instruments |  |  |  |  |
Amount hedged per month | $ |  |  |  |  | $ 20.0
Average foreign exchange rate | item |  | 1.34 |  |  |
Purchased put options [Member] |  |  |  |  |
Disclosure of derivative instruments |  |  |  |  |
Strike price of copper price option contracts | oz | 2.50 |  |  |  |
Selling call options [Member] |  |  |  |  |
Disclosure of derivative instruments |  |  |  |  |
Strike price of copper price option contracts | lb | 3.00 |  |  |  |
Copper price option contracts [Member] |  |  |  |  |
Disclosure of derivative instruments |  |  |  |  |
Quantity of production |  | 21,600 | 47,600,000 |  |
Gold price option contracts [Member] |  |  |  |  |
Disclosure of derivative instruments |  |  |  |  |
Quantity of production | oz |  |  |  | 192,000 |

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- Details
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- Details
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