Note 2 - Business Segments and Sales of Products - Sales of Products (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	$ 178,131	$ 191,242	$ 377,631	$ 377,741
Less: Smelter and refining charges	(12,220)	(13,316)	(28,193)	(25,519)
Net sales	177,753	191,242	376,744	377,741
Silver Contracts [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	79,489	70,050	161,022	136,382
Gold [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	62,924	82,018	138,010	159,186
Lead [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	21,657	21,314	47,059	40,878
Zinc [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Net sales	$ 25,903	$ 31,176	$ 58,846	$ 66,814