Note 11 - Derivative Instruments (Details) - Jun. 30, 2015 - USD ($) $ in Millions	Total	Total
Unsettled Sales and Forecasted Future Concentrate Contracts [Member] \| Other Current Assets [Member]
Note 11 - Derivative Instruments (Details) [Line Items]
Derivative Asset, Current	$ 3.0	$ 3.0
Derivative Liability, Current	1.1	1.1
Unsettled Sales and Forecasted Future Concentrate Contracts [Member] \| Other Noncurrent Assets [Member]
Note 11 - Derivative Instruments (Details) [Line Items]
Derivative Asset, Noncurrent	0.5	0.5
Unsettled Concentrate Sales Contracts [Member]
Note 11 - Derivative Instruments (Details) [Line Items]
Derivative, Gain on Derivative		1.4
Forecasted Future Concentrate Contracts [Member]
Note 11 - Derivative Instruments (Details) [Line Items]
Derivative, Gain on Derivative		4.9
Proceeds from Derivative Instrument, Operating Activities	$ 12.0
Forecasted Future Concentrate Contracts [Member] \| Gains Realized on Settled Contracts [Member]
Note 11 - Derivative Instruments (Details) [Line Items]
Derivative, Gain on Derivative		$ 15.0

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The amount of proceeds from a derivative instrument classified as operating activities.

+ References

No definition available.

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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.

+ References

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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 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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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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