Note 4 - Business Segments, Sales of Products and Significant Customers (Details Textual) $ in Thousands, lb in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) oz lb	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Number of Reportable Segments	4
Derivative, Loss on Derivative	$ 500	$ 16,400	$ 1,300
Accounts Receivable, after Allowance for Credit Loss, Current, Total	$ 36,437	27,864
Accounts Receivable, Allowance for Credit Loss, Ending Balance		$ 0
Silver Contracts [Member]
Metals Contained in Concentrates (Ounce) | oz	2.1
Gold [Member]
Metals Contained in Concentrates (Ounce) | oz	6,224
Zinc [Member]
Metals Contained in Concentrates (Ounce) | lb	27.5
Lead [Member]
Metals Contained in Concentrates (Ounce) | lb	12.7