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Commitments (Details) oz in Millions, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) oz | Dec. 31, 2016 USD ($)
Commitments [Line Items] |  |
Capital purchases commitments | $ 21.8 | $ 2.8
Royalties | 15.6 | 13.3
Royal Gold [Member] |  |
Commitments [Line Items] |  |
Extraordinary mining duty tax | 1.0 | 0.9
Island Gold [Member] |  |
Commitments [Line Items] |  |
Royalties | $ 0.6 |
Production Royalty [Member] | Royal Gold [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 5.00% |
Quantity of production subject to royalty | oz | 2.0 |
Actual production quantity | oz | 1.8 |
Royalties | $ 9.6 | 8.7
Net Smelter Royalty [Member] | AuRico Metals [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 1.50% |
Royalties | $ 3.9 | 3.2
Net Smelter Royalty [Member] | Island Gold [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 2.00% |
Other Royalties [Member] | AuRico Metals [Member] |  |
Commitments [Line Items] |  |
Royalties | $ 0.5 | $ 0.5
Turkey [Member] | Net Smelter Royalty [Member] | Third Party [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 2.00% |
Turkey [Member] | State Royalty [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 3.00% |
Lochalsh [Member] | Production Royalty [Member] | Island Gold [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 3.00% |
Goudreau [Member] | Net Profit Interest [Member] | Island Gold [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 15.00% |
Goudreau Lake [Member] | Production Royalty [Member] | Island Gold [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 4.38% |
Goudreau Lake [Member] | Net Profit Interest [Member] | Island Gold [Member] |  |
Commitments [Line Items] |  |
Royalty rate | 10.38% |

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