Note 2 - Business Segments and Sales of Products - Sales of Products (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Net sales	$ 191,242	$ 217,983	$ 377,741	$ 428,835
Less: Smelter and refining charges	(13,316)	(13,120)	(25,519)	(26,521)
Silver Contracts [Member]
Net sales	70,050	92,765	136,382	170,525
Gold [Member]
Net sales	82,018	86,078	159,186	187,487
Lead [Member]
Net sales	21,314	22,223	40,878	38,116
Zinc [Member]
Net sales	$ 31,176	$ 30,037	$ 66,814	$ 59,228