Note 8 - Derivative Instruments (Details Textual) $ in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025 USD ($) Contract	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) Contract	Jun. 30, 2024 USD ($)	Jun. 30, 2025 CAD ($) Contract
Derivative [Line Items]
Maximum Allocation of Forecasted CAD-demonimated Operating Costs	75.00%		75.00%		75.00%
Forecasted CAD-denominated Operating Costs to be Hedged, Term (Year)			5 years
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	$ 1.0	$ 1.1	$ 2.8	$ 1.5
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	13.4		13.4
Derivative, Gain (Loss) on Derivative, Net, Total	$ 3.8	12.5	1.3	9.4
Other Comprehensive Income (Loss) [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total			$ 0.2
Foreign Exchange Forward [Member]
Derivative [Line Items]
Derivative, Notional Amount					$ 6.1
Derivative, Forward Exchange Rate	0.013718		0.013718		0.013718
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	$ 1.4		$ 1.4
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	$ 1.2		$ 1.2
Foreign Exchange Forward [Member] | Casa Berardi [Member]
Derivative [Line Items]
Derivative, Notional Amount					$ 9.5
Derivative, Forward Exchange Rate	0.013421		0.013421		0.013421
Foreign Exchange Forward [Member] | Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount					$ 40.3
Derivative, Forward Exchange Rate	0.0000014049		0.0000014049		0.0000014049
Foreign Exchange Forward [Member] | Casa Berardi and Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount					$ 131.5
Derivative, Forward Exchange Rate	0.01351		0.01351		0.01351
Foreign Exchange Forward [Member] | Casa Berardi and Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount					$ 6.7
Derivative, Forward Exchange Rate	0.013975		0.013975		0.013975
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Casa Berardi [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held, Total | Contract	274		274		274
Derivative, Notional Amount	$ 170.0		$ 170.0		$ 234.1
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	5.4	0.5	5.5	2.4
Price Risk Derivative [Member]
Derivative [Line Items]
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	14.5		14.5
Settlement Under Collars [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total	0.8		0.2
Unsettled Concentrate Sales Contracts [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total	3.3	12.5	2.0	9.4
Price Risk Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	3.5	$ 3.0	5.7	$ 4.9
Commodity Contract [Member]
Derivative [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset of Collateral, Total	3.0		3.0
Derivative, Fair Value, Obligations Under the Agreements	$ 3.0		3.0
Zinc Contract 2022 [Member] | Other Comprehensive Income (Loss) [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total			17.4
Zinc and Lead Contract 2023 [Member] | Other Comprehensive Income (Loss) [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total			$ 8.5