Note 8 - Derivative Instruments (Details Textual) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) Contract	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) Contract	Sep. 30, 2022 USD ($)
Derivative [Line Items]
Maximum Allocation of Forecasted CAD-demonimated Operating Costs	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	$ 600		$ 2,500
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	11,700		11,700
Other Comprehensive Income (Loss) [Member]
Derivative [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	2,900		2,900
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	4,900		4,900
Foreign Exchange Forward [Member] | Casa Berardi [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 52,600		$ 52,600
Derivative, Forward Exchange Rate	0.000001357		0.000001357
Foreign Exchange Forward [Member] | Casa Berardi [Member] | Minimum [Member]
Derivative [Line Items]
Derivative, Forward Exchange Rate	1,275.5000		1,275.5000
Foreign Exchange Forward [Member] | Casa Berardi [Member] | Maximum [Member]
Derivative [Line Items]
Derivative, Forward Exchange Rate	13,725		13,725
Foreign Exchange Forward [Member] | Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 27,100		$ 27,100
Derivative, Forward Exchange Rate	0.0000013533		0.0000013533
Foreign Exchange Forward [Member] | Casa Berardi and Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 406,300		$ 406,300
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Casa Berardi [Member]
Derivative [Line Items]
Derivative, Number of Instruments Held, Total | Contract	642		642
Derivative, Notional Amount	$ 510,800		$ 510,800
Foreign Exchange Forward [Member] | Designated as Hedging Instrument [Member] | Casa Berardi and Keno Hill [Member]
Derivative [Line Items]
Derivative, Notional Amount	383,600		383,600
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	3,200		100
Price Risk Derivative [Member]
Derivative [Line Items]
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	15,100		15,100
Unsettled Concentrate Sales Contracts [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total		$ 4,000	13,100
Price Risk Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net		6,700	13,000
Forecasted Future Concentrate Contracts [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net, Total	1,600	$ 1,600	8,100	$ 8,100
Commodity Contract [Member]
Derivative [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset of Collateral, Total	7,100		7,100
Derivative, Fair Value, Obligations Under the Agreements	$ 7,100		$ 7,100