The amount of required settlement obligation under the agreements at termination.

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Period within which forecasted CAD (Canadian dollar) denominated operating costs will be hedged.

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Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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-Publisher SEC
-Name Regulation S-X (SX)
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-Article 12
-Section 13
-Sentence Column B

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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.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Contractual rate at which a foreign currency can be purchased or sold.

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Amount of increase in the fair value of derivatives recognized in the income statement.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of asset associated with financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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The number of derivative instruments of a particular group held by the entity.

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The net gain (loss) relating to components of the gain (loss) on foreign currency cash flow hedging instruments excluded from the assessment of hedge effectiveness. Recognized in earnings.

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The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

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Note 11 - Derivative Instruments (Details Textual) $ in Thousands, $ in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2018 CAD ($)	Mar. 31, 2018 MXN ($)
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, Ending Balance	$ 3,000
Gain (Loss) on Sale of Derivatives	4,007	$ (7,809)
Gain (Loss) on Components Excluded from Assessment of Foreign Currency Cash Flow Hedge Effectiveness	15
Derivative, Gain on Derivative	600
Derivative Liability, Fair Value, Amount Not Offset Against Collateral, Total	10,900
Derivative, Fair Value, Obligations Under the Agreements	10,900
Cost of Sales [Member]
Gain (Loss) on Sale of Derivatives	500
Other Comprehensive Income (Loss) [Member]
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	800
Foreign Exchange Contract [Member] \| Other Current Assets [Member]
Derivative Asset, Current	1,100
Foreign Exchange Contract [Member] \| Other Noncurrent Assets [Member]
Derivative Assets, Noncurrent, Total	2,000
Foreign Exchange Contract [Member] \| Other Current Liabilities [Member]
Derivative Liability, Current	$ 200
Foreign Exchange Contract [Member] \| Casa Berardi [Member] \| Minimum [Member] \| United States of America, Dollars
Derivative, Forward Exchange Rate	1.2729		1.2729	1.2729
Foreign Exchange Contract [Member] \| Casa Berardi [Member] \| Maximum [Member] \| United States of America, Dollars
Derivative, Forward Exchange Rate	1.336		1.336	1.336
Foreign Exchange Contract [Member] \| Casa Berardi [Member] \| Designated as Hedging Instrument [Member]
Derivative, Number of Instruments Held, Total	120		120	120
Derivative, Notional Amount	$ 220,800		$ 285.4
Foreign Exchange Contract [Member] \| San Sebastian [Member] \| Minimum [Member] \| United States of America, Dollars
Derivative, Forward Exchange Rate	19.175		19.175	19.175
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, Total	36		36	36
Derivative, Notional Amount	$ 13,900			$ 276.6
Commodity Contract [Member] \| Other Current Assets [Member]
Derivative Asset, Current	300
Commodity Contract [Member] \| Other Noncurrent Assets [Member]
Derivative Assets, Noncurrent, Total	300
Commodity Contract [Member] \| Other Current Liabilities [Member]
Derivative Liability, Current	6,800
Derivative Liability, Fair Value, Gross Asset	100
Commodity Contract [Member] \| Other Noncurrent Liabilities [Member]
Derivative Liability, Fair Value, Gross Asset	3,100
Derivative Liability, Noncurrent	300
Unsettled Concentrate Sales Contracts [Member]
Derivative, Gain on Derivative	600
Forecasted Future Concentrate Contracts [Member]
Derivative, Gain on Derivative	$ 4,000