Note 9 - Derivative Instruments - Summary of Forward Sales Contracts (Details) oz in Thousands, lb in Thousands	12 Months Ended
	Dec. 31, 2022 lb oz $ / $ $ / oz	Dec. 31, 2021 oz lb $ / $ $ / oz
Silver 2022 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz		1,814
Underlying, Derivative Mass | $ / oz		23.02
Silver 2023 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	3,124
Underlying, Derivative Mass | $ / oz	21.55
Gold 2022 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz		6
Underlying, Derivative Mass | $ / oz		1,812
Gold 2023 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	8
Underlying, Derivative Mass | $ / oz	1,795
Zinc 2022 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass		13,371
Underlying, Derivative Mass | $ / $		1.39
Lead 2022 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass		4,575
Underlying, Derivative Mass | $ / $		0.96
Zinc 2022 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass		57,706
Underlying, Derivative Mass | $ / $	1.34	1.28
Lead 2022 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass		59,194
Underlying, Derivative Mass | $ / $	1.00	0.98
Zinc 2023 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass	37,533	76,280
Underlying, Derivative Mass | $ / $		1.29
Zinc 2023 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass	18,629
Underlying, Derivative Mass | $ / $	1.38
Zinc 2024 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass	0
Lead 2023 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass	75,618	71,650
Underlying, Derivative Mass | $ / $		1.00
Lead 2023 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass	11,960
Underlying, Derivative Mass | $ / $	0.98
Lead 2024 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass	45,856
Underlying, Derivative Mass | $ / $	0.99