Note 2 - Business Segments and Sales of Products - Sales of Products (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Sales of products	$ 210,852	$ 136,925
Less: Smelter and refining charges	(13,400)	(15,069)
Silver Contracts [Member]
Sales of products	77,760	37,572
Gold [Member]
Sales of products	101,408	90,694
Lead [Member]
Sales of products	15,893	6,420
Zinc [Member]
Sales of products	$ 29,191	$ 17,308

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