Note 8 - Derivative Instruments - Summary of Forward Sales Contracts (Details) oz in Thousands, lb in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023 lb oz $ / $ $ / oz	Dec. 31, 2022 oz lb $ / $ $ / oz
Silver 2022 Settlements for Provisional Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | oz	3,350	3,124
Underlying, Derivative Mass | $ / oz	22.27	21.55
Gold 2022 Settlements for Provisional Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | oz	8	8
Underlying, Derivative Mass | $ / oz	1,883	1,795
Zinc 2022 Settlements for Provisional Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	15,543	18,629
Underlying, Derivative Mass | $ / $	1.35	1.38
Lead 2022 Settlements for Provisional Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	18,133	11,960
Underlying, Derivative Mass | $ / $	1.01	0.98
Silver 2023 Settlements for Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | oz	0	0
Gold 2023 Settlements for Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | oz	0	0
Zinc 2023 Settlements for Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass	29,873	37,533
Underlying, Derivative Mass | $ / $	1.47	1.34
Lead 2023 Settlements for Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass	38,581	75,618
Underlying, Derivative Mass | $ / $	1.00	1.00
Silver 2024 Settlements for Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | oz	0	0
Gold 2024 Settlements for Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | oz	0	0
Zinc 2024 Settlements for Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass	1,764	0
Underlying, Derivative Mass | $ / oz	1.31
Lead 2024 Settlements for Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	75,178	45,856
Underlying, Derivative Mass | $ / $	0.98	0.99
Lead 2025 Settlements For Forecasted Sales [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass | lb	882
Underlying, Derivative Mass | $ / $	0.97