Note 8 - Derivative Instruments (Details Textual) $ in Millions, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2024 oz $ / oz	Sep. 30, 2024 USD ($) Contract	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Contract	Sep. 30, 2023 USD ($)	Sep. 30, 2024 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		$ 1.5	$ 0.6	$ 3.0	$ 2.5
Gain (Loss) on Components Excluded from Assessment of Foreign Currency Cash Flow Hedge Effectiveness		0.0	0.0	0.0	0.0
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months		4.5		4.5
Derivative, Gain (Loss) on Derivative, Net, Total		0.6	4.0	8.8	13.1
Put Option
Derivative [Line Items]
Derivative, Notional Amount		0.1		0.1
Other Comprehensive Income (Loss) [Member]
Derivative [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months		1.5		1.5
Casa Berardi [Member] | Put Option
Derivative [Line Items]
Derivative, Notional Amount		$ 0.1		$ 0.1
Designated as Hedging Instrument [Member] | Put Option
Derivative [Line Items]
Derivative instrument gold put option purchased | oz	26,900
Price per ounce | $ / oz	2,100
Foreign Exchange Forward [Member]
Derivative [Line Items]
Derivative, Notional Amount						$ 8.9
Derivative, Forward Exchange Rate		0.01358		0.01358		0.01358
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax		$ 1.6		$ 1.6
Foreign Exchange Forward [Member] | Casa Berardi [Member]
Derivative [Line Items]
Derivative, Notional Amount						$ 19.5
Derivative, Forward Exchange Rate		0.01347		0.01347		0.01347
Foreign Exchange Forward [Member] | Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount						$ 12.2
Derivative, Forward Exchange Rate		0.01356		0.01356		0.01356
Foreign Exchange Forward [Member] | Casa Berardi and Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount						$ 194.7
Derivative, Forward Exchange Rate		0.01327		0.01327		0.01327
Foreign Exchange Forward [Member] | Casa Berardi and Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount						$ 1.6
Derivative, Forward Exchange Rate		0.013608		0.013608		0.013608
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Casa Berardi [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held, Total | Contract		359		359		359
Derivative, Notional Amount		$ 178.0		$ 178.0		$ 236.9
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives		0.5	3.2	1.9	0.1
Price Risk Derivative [Member]
Derivative [Line Items]
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax		5.6		5.6
Unsettled Concentrate Sales Contracts [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total		0.6	4.0	8.8	13.1
Price Risk Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net		2.1	$ 6.7	7.1	$ 13.0
Commodity Contract [Member]
Derivative [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset of Collateral, Total		5.8		5.8
Derivative, Fair Value, Obligations Under the Agreements		$ 5.8		5.8
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