Note 2 - Business Segments and Sales of Products - Sales of Products (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Net sales	$ 186,499	$ 210,852
Less: Smelter and refining charges	(12,203)	(13,400)
Silver Contracts [Member]
Net sales	66,332	77,760
Gold [Member]
Net sales	77,168	101,408
Lead [Member]
Net sales	19,564	15,893
Zinc [Member]
Net sales	$ 35,638	$ 29,191

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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+ Details