Note 8 - Derivative Instruments - Summary of Forward Sales Contracts (Details) oz in Thousands, lb in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022 lb oz $ / lb $ / oz	Dec. 31, 2021 lb oz $ / lb $ / oz
Silver 2022 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	2,235	1,814
Underlying, Derivative Mass | $ / oz	19.54	23.02
Gold 2022 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	1,840	6
Underlying, Derivative Mass | $ / oz	1,760	1,812
Zinc 2022 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	18,739	13,371
Underlying, Derivative Mass | $ / lb	1.3	1.39
Lead 2022 Settlements for Provisional Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	14,991	4,575
Underlying, Derivative Mass | $ / lb	0.96	0.96
Silver 2022 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	2,235	0
Gold 2022 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	1,840	0
Zinc 2022 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	8,763	57,706
Underlying, Derivative Mass | $ / lb	1.32	1.28
Lead 2022 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	1,984	59,194
Underlying, Derivative Mass | $ / lb	0.97	0.98
Silver 2023 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	0	0
Gold 2023 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	0	0
Zinc 2023 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	71,209	76,280
Underlying, Derivative Mass | $ / lb	1.3	1.29
Lead 2023 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	75,618	71,650
Underlying, Derivative Mass | $ / lb	1	1
Silver 2024 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	0
Gold 2024 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	0
Zinc 2024 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	78,760
Underlying, Derivative Mass | $ / lb	1.34
Lead 2024 Settlements for Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	31,526
Underlying, Derivative Mass | $ / lb	1
Silver 2025 Settlements For Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	0
Gold 2025 Settlements For Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | oz	0
Zinc 2025 Settlements For Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	2,480
Underlying, Derivative Mass | $ / lb	1.33
Lead 2025 Settlements For Forecasted Sales [Member]
Derivative, Nonmonetary Notional Amount, Mass | lb	0