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RECLAMATION AND CLOSURE COST OBLIGATIONS (Details Textual) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Disclosure of reclamation and closure cost obligations [Line Items] |  |
Revisions to expected cash flows related to reclamation obligation | $ 55.2 | $ 15.5
Percentage of annual fees of the value of outstanding letters of credit | 1.50% |
Rainy River [Member] |  |
Disclosure of reclamation and closure cost obligations [Line Items] |  |
Adjustments for increase (decrease) in other liabilities | $ 41.4 |
Mesquite [Member] |  |
Disclosure of reclamation and closure cost obligations [Line Items] |  |
Adjustments for increase (decrease) in other liabilities | 6.6 |
Letters Of Credit [Member] |  |
Disclosure of reclamation and closure cost obligations [Line Items] |  |
Exposure to credit risk on loan commitments and financial guarantee contracts | 137.8 | 113.0
Surity Bonds [Member] |  |
Disclosure of reclamation and closure cost obligations [Line Items] |  |
Exposure to credit risk on loan commitments and financial guarantee contracts | $ 19.6 | $ 14.8
Bottom of range [member] |  |
Disclosure of reclamation and closure cost obligations [Line Items] |  |
Discount rate applied to cash flow projections | 1.90% | 1.40%
Description of inflation rates applied to cash flow projections | 1.70% | 1.00%
Top of range [member] |  |
Disclosure of reclamation and closure cost obligations [Line Items] |  |
Discount rate applied to cash flow projections | 6.00% | 6.00%
Description of inflation rates applied to cash flow projections | 3.30% | 3.30%

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