Note 9 - Fair Value Measurement - Assets and Liabilities Accounted for at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Receivables from provisional concentrate sales	$ 12,846	$ 8,149
Fair Value, Recurring [Member]
Total assets	199,675	267,177
Total liabilities	11,334	37,881
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Recurring [Member]
Money market funds and other bank deposits	144,669	210,010
Equity securities	13,299	14,470
Certificates of deposit and other deposits	1,246	1,053
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Recurring [Member]
Receivables from provisional concentrate sales	12,477	36,437
Foreign exchange contracts	591	5,207
Metal forward and put option contracts	27,393	0
Foreign exchange contracts	11,334	8
Metal forward and put option contracts	$ 0	$ 37,873

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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