Note 11 - Fair Value Measurement - Assets and Liabilities Accounted for at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Receivables from provisional concentrate sales	$ 17,110	$ 17,538
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Money market funds and other bank deposits	241,558	26,868
Equity securities	107,486	33,158
Certificates of deposit and other deposits	1,174	1,177
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Receivables from provisional concentrate sales	170,230	31,515
Metal forward contracts	$ 15,840	$ 18,039
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Assets	Assets
Foreign exchange contracts	$ 1,127	$ 0
Metal forward contracts	$ 38,273	$ 0
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Liabilities	Liabilities
Foreign exchange contracts	$ 829	$ 10,176