Note 12 - Assets and Liabilities Accounted for at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents:
Money market funds and other bank deposits	$ 134,018	$ 155,209
Available for sale securities:
Equity securities – mining industry	2,086	1,515
Restricted cash balances:
Certificates of deposit and other bank deposits	4,899	999
Fair Value, Inputs, Level 2 [Member]
Trade accounts receivable:
Receivables from provisional concentrate sales	30,127	13,490
Derivative contracts:
Metal forward contracts	453	283
Receivables from provisional concentrate sales	16,786	16,401
Total assets	$ 171,130	$ 171,213

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Amount of deposits in accounts that offer many of the same services as checking accounts although transactions may be somewhat more limited, share some of the characteristics of a money market fund and are insured by the Federal government, also known as money market accounts.

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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. Includes liabilities 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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Amount due from parties in nontrade transactions, classified as other.

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Fair value of investments in trading equity securities and other forms of trading securities that provide ownership interests.

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