Note 2 - Business Segments and Sales of Products - Sales of Products (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	$ 199,500	$ 186,499
Less: Smelter and refining charges	(15,973)	(12,203)
Net sales	198,991	186,499
Silver Contracts [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	81,532	66,332
Gold [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	75,087	77,168
Lead [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	25,402	19,564
Zinc [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	$ 32,943	$ 35,638