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IMPAIRMENT (Tables) | 12 Months Ended
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Dec. 31, 2017
Disclosure of impairment loss and reversal of impairment loss [abstract] |
Disclosure of impairment loss and reversal of impairment loss [text block] | For the year ended December 31, 2017, the Company recorded an after-tax impairment loss of $181.0 million within net loss, as noted below:
| Year ended December 31, 2017
(in millions of U.S. dollars) |  |  |  | Rainy River
Impairment charge included within NET LOSS |  |  |
Rainy River depletable mining properties |  |  |  | 268.4
Tax recovery |  |  |  | (87.4)
Total impairment charge after tax |  |  |  | 181.0
For the year ended December 31, 2016, the Company recorded an impairment charge of $6.4 million within net loss, as noted below:
| Year ended December 31, 2016
(in millions of U.S. dollars) |  |  |  | Rio Figueroa NSR
Impairment charge included within NET LOSS |  |  |
Exploration and evaluation assets |  |  |  | 6.4
Disclosure of impairment analysis, of commodity prices and exchange rate [text block] | the following commodity prices and exchange rate assumptions were used:
As at December 31, 2017 | As at December 31, 2016
(in U.S. dollars, except where noted) | 2018 - 2022 Average | Long term | 2017 - 2021 Average | Long term
Commodity prices |  |  |  |
Gold ($/ounce) | 1,300 | 1,300 | 1,325 | 1,300
Silver ($/ounce) | 19.16 | 19.25 | 19.66 | 20.00
Exchange rates |  |  |  |
CAD:USD | 1.24 | 1.24 | 1.31 | 1.30
Disclosure Of Detailed Information About Sensitivity Analysis On Key Assumptions Used In Determining Impairment Loss [text block] | Any variation in the key assumptions used to determine fair value would result in a change of the assessed fair value. It is estimated that changes in the key assumptions would have the following approximate impact on the fair value of the Rainy River CGU at December 31, 2017:
| As at December 31, 2017
(in millions of U.S. dollars) |  |  |  | Rainy River
Impact of changes in the key assumptions used to determine fair value |  |
$100 per ounce change in gold price |  |  |  | 235.1
0.5% change in discount rate |  |  |  | 25.9
5% change in exchange rate |  |  |  | 106.5
5% change in operating costs |  |  |  | 90.3
5% change in in-situ ounces |  |  |  | 20.2

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