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Note 10 - Derivative Instruments (Details Textual) $ in Thousands, MXN in Millions, CAD in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2017 CAD | Dec. 31, 2017 MXN
Maximum Allocation of Forecasted CAD-demonimated Operating Costs | 75.00% |  |  | 75.00% | 75.00%
Forecasted CAD-denominated Operating Costs to be Hedged, Term | 5 years |  |  |  |
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax | $ 5,000 |  |  |  |
Gain (Loss) on Sale of Derivatives | (21,250) | $ 4,423 | $ 8,252 |  |
Gain (Loss) on Components Excluded from Assessment of Foreign Currency Cash Flow Hedge Effectiveness | 5 |  |  |  |
Derivative, Loss on Derivative | 6,000 | $ 14,200 |  |  |
Derivative Liability, Fair Value, Amount Not Offset Against Collateral | 800 |  |  |  |
Derivative, Fair Value, Obligations Under the Agreements | 800 |  |  |  |
Cost of Sales [Member] |  |  |  |  |
Gain (Loss) on Sale of Derivatives | 1,100 |  |  |  |
Other Comprehensive Income (Loss) [Member] |  |  |  |  |
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months | 2,100 |  |  |  |
Foreign Exchange Contract [Member] | Other Current Assets [Member] |  |  |  |  |
Derivative Asset, Current | 2,300 |  |  |  |
Foreign Exchange Contract [Member] | Other Current Liabilities [Member] |  |  |  |  |
Derivative Liability, Current | 400 |  |  |  |
Foreign Exchange Contract [Member] | Other Noncurrent Assets [Member] |  |  |  |  |
Derivative Asset, Noncurrent | 2,700 |  |  |  |
Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member] |  |  |  |  |
Derivative Liability, Noncurrent | $ 300 |  |  |  |
Foreign Exchange Contract [Member] | Casa Berardi [Member] | Maximum [Member] | United States of America, Dollars |  |  |  |  |
Derivative, Forward Exchange Rate | 1.338 |  |  | 1.338 | 1.338
Foreign Exchange Contract [Member] | Casa Berardi [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative, Number of Instruments Held | 96 |  |  | 96 | 96
Derivative, Notional Amount | $ 164,500 |  |  | CAD 213.1 |
Foreign Exchange Contract [Member] | Casa Berardi [Member] | Designated as Hedging Instrument [Member] | Minimum [Member] |  |  |  |  |
Derivative, Forward Exchange Rate | 1.2787 |  |  | 1.2787 | 1.2787
Foreign Exchange Contract [Member] | San Sebastian [Member] | Minimum [Member] | United States of America, Dollars |  |  |  |  |
Derivative, Forward Exchange Rate | 18.8317 |  |  | 18.8317 | 18.8317
Foreign Exchange Contract [Member] | San Sebastian [Member] | Maximum [Member] | United States of America, Dollars |  |  |  |  |
Derivative, Forward Exchange Rate | 20.855 |  |  | 20.855 | 20.855
Foreign Exchange Contract [Member] | San Sebastian [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative, Number of Instruments Held | 25 |  |  | 25 | 25
Derivative, Notional Amount | $ 14,100 |  |  |  | MXN 278.2
Commodity Contract [Member] | Other Current Liabilities [Member] |  |  |  |  |
Derivative Liability, Current | 10,300 |  |  |  |
Derivative Liability, Fair Value, Gross Asset | 200 |  |  |  |
Commodity Contract [Member] | Other Noncurrent Liabilities [Member] |  |  |  |  |
Derivative Liability, Noncurrent | 5,200 |  |  |  |
Unsettled Concentrate Sales Contracts [Member] |  |  |  |  |
Derivative, Loss on Derivative | 6,000 |  |  |  |
Forecasted Future Concentrate Contracts [Member] |  |  |  |  |
Derivative, Loss on Derivative | $ 21,300 |  |  |  |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e681-108580 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80784-113994 + Details
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