Note 11 - Fair Value Measurement - Assets and Liabilities Accounted for at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Receivables from provisional concentrate sales	$ 17,538	$ 13,691
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Money market funds and other bank deposits	26,868	106,374
Equity securities	33,158	32,284
Certificates of deposit and other deposits	1,177	1,165
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Receivables from provisional concentrate sales	31,515	17,940
Metal forward contracts	$ 18,039	$ 4,698
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Assets	Assets
Foreign exchange contracts	$ 0	$ 4,657
Metal forward contracts	$ 0	$ 40
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Liabilities	Liabilities
Foreign exchange contracts	$ 10,176	$ 1,508