Note 8 - Derivative Instruments (Details Textual) $ in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) Contract	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) Contract	Jun. 30, 2022 USD ($)	Jun. 30, 2023 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	$ 1,100		$ 2,000
Gain (Loss) on Components Excluded from Assessment of Foreign Currency Cash Flow Hedge Effectiveness			0
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	19,000		19,000
Other Comprehensive Income (Loss) [Member]
Derivative [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	900		900
Derivative, Gain (Loss) on Derivative, Net, Total	17,400		7,600
Foreign Exchange Forward [Member]
Derivative [Line Items]
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	700		700
Foreign Exchange Forward [Member] | Casa Berardi [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 62,300		$ 62,300		$ 353.0
Derivative, Forward Exchange Rate	0.00000135		0.00000135		0.00000135
Foreign Exchange Forward [Member] | Casa Berardi [Member] | Minimum [Member]
Derivative [Line Items]
Derivative, Forward Exchange Rate	1,275.5000		1,275.5000		1,275.5000
Foreign Exchange Forward [Member] | Casa Berardi [Member] | Maximum [Member]
Derivative [Line Items]
Derivative, Forward Exchange Rate	13,738		13,738		13,738
Foreign Exchange Forward [Member] | Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 93,000		$ 93,000
Derivative, Forward Exchange Rate	0.00000136		0.00000136		0.00000136
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Casa Berardi [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held, Total | Contract	507		507		507
Derivative, Notional Amount	$ 396,600		$ 396,600		$ 527.2
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	2,400		3,100
Price Risk Derivative [Member]
Derivative [Line Items]
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	26,700		26,700
Unsettled Concentrate Sales Contracts [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total	8,200	$ 8,200	9,100	$ 9,100
Price Risk Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	3,300	3,300	6,300	6,300
Forecasted Future Concentrate Contracts [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total	11,300	$ 11,300	6,600	$ 6,600
Commodity Contract [Member]
Derivative [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset of Collateral, Total	2,300		2,300
Derivative, Fair Value, Obligations Under the Agreements	$ 2,300		$ 2,300