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DERIVATIVE INSTRUMENTS (Details Textual) $ in Millions | 1 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Jun. 30, 2017 USD ($) $ / Ounce-oz | Dec. 31, 2017 lb $ / Pound-lb gal | Jun. 30, 2017 Ounces lb $ / Ounce-oz $ / Pound-lb | Dec. 31, 2016 Ounces $ / Ounce-oz gal | Dec. 31, 2017 USD ($) $ / Pound-lb gal | Dec. 31, 2016 USD ($) gal | Oct. 31, 2017 lb | Sep. 30, 2016 $ / Ounce-oz
Disclosure of derivative instruments [Line Items] |  |  |  |  |  |  |  |
Volume of diesel considered for settlement | gal |  | 1.0 |  | 5.5 | 1.0 | 5.5 |  |
Gain Loss On Hedging Instrument |  |  |  |  | $ 0.3 | $ 2.5 |  |
Strike price of put options at the time of purchasing | $ / Ounce-oz |  |  |  | 1,200 |  |  |  |
Strike price of call options at the time of selling | $ / Ounce-oz |  |  |  | 1,400 |  |  |  |
Volume of gold production |  | 120,000 |  | 270,000 |  |  |  |
Number of ounces exercised through put options |  |  |  |  | 140,000 |  |  |
Revenue from contracts with customers |  |  |  |  | $ 7.5 |  |  |
Loss on settlement of gold price option contracts |  |  |  |  | 11.0 |  |  |
Gain from gold price option contracts |  |  |  |  | 4.6 |  |  |
Gain loss on revaluation of gold price option contracts |  |  |  |  | (13.9) | $ 10.5 |  |
Loss from Copper forward contracts |  |  |  |  | $ 0.9 |  |  |
Purchased put options [Member] |  |  |  |  |  |  |  |
Disclosure of derivative instruments [Line Items] |  |  |  |  |  |  |  |
Strike price of options | $ / Ounce-oz | 1,250 |  | 1,250 |  |  |  |  | 1,300
Strike price of copper price option contracts | lb |  |  |  |  |  |  | 3.00 |
Written call options [Member] |  |  |  |  |  |  |  |
Disclosure of derivative instruments [Line Items] |  |  |  |  |  |  |  |
Strike price of options | $ / Ounce-oz | 1,400 |  | 1,400 |  |  |  |  | 1,400
Strike price of copper price option contracts | lb |  |  |  |  |  |  | 3.37 |
Gold Option Contracts [Member] |  |  |  |  |  |  |  |
Disclosure of derivative instruments [Line Items] |  |  |  |  |  |  |  |
Cash payments for futures contracts, forward contracts, option contracts and swap contracts, classified as investing activities | $ 0.9 |  |  |  |  |  |  |
Forward Looking Disclosure [Member] |  |  |  |  |  |  |  |
Disclosure of derivative instruments [Line Items] |  |  |  |  |  |  |  |
Volume of gold production | Ounces |  |  | 120,000 |  |  |  |  |
Volume of copper per month | lb |  | 7,300,000 | 5,300,000 |  |  |  |  |
Fixed price per pound of copper | $ / Pound-lb |  | 2.73 | 2.52 |  | 120,000 |  |  |
Loss from Copper forward contracts |  |  |  |  | $ 0.3 |  |  |

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