Note 2 - Business Segments and Sales of Products - Sales of Products (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Total sales	$ 181,906	$ 146,339	$ 559,537	$ 524,080
Less: Smelter and refining charges	(12,550)	(13,023)	(40,743)	(38,543)
Silver Contracts [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total sales	74,425	45,924	235,447	182,306
Gold [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total sales	70,206	69,289	208,216	228,475
Lead [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total sales	15,719	16,033	62,778	56,912
Zinc [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total sales	33,066	28,051	91,912	94,865
Total Metal [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total sales	180,866	146,274	557,610	524,015
Environmental Remediation Services [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Total sales	$ 1,040	$ 65	$ 1,927	$ 65