Note 12 - Fair Value Measurement (Details) - Assets and Liabilities Accounted for at Fair Value (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Trade accounts receivable:
Receivables from provisional concentrate sales	$ 9,767	$ 20,893
Derivative contracts:
Total assets	247,861	246,544
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents:
Money market funds and other bank deposits	222,360	212,175
Available for sale securities:
Equity securities – mining industry	7,022	7,019
Restricted cash balances:
Certificates of deposit and other bank deposits	883	5,217
Fair Value, Inputs, Level 2 [Member]
Trade accounts receivable:
Receivables from provisional concentrate sales	17,433	17,672
Derivative contracts:
Metal forward contracts	163	4,461
Derivative contracts:
Metal forward contracts	$ 2,160

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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. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value portion of other assets.

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