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Note 11 - Derivative Instruments (Details Textual) $ / item in Thousands, $ in Thousands, $ in Thousands, $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 CAD ($)	Jun. 30, 2020 MXN ($)	May 07, 2020 $ / item	Dec. 31, 2019 USD ($)
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
Derivative Liability, Current	$ 13,779					$ 6,170
Derivative Liability, Noncurrent	5,282					$ 1,044
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax, Ending Balance	9,300
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	4,000
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	1,900
Gain (Loss) on Components Excluded from Assessment of Foreign Currency Cash Flow Hedge Effectiveness	0
Derivative, Gain (Loss) on Derivative, Net, Total	(11,188)	$ 6,101
Derivative Liability, Fair Value, Amount Offset Against Collateral, Total	19,800
Derivative, Fair Value, Obligations Under the Agreements	19,800
Foreign Exchange Contract [Member] \| Other Current Assets [Member]
Derivative Asset, Current	100
Foreign Exchange Contract [Member] \| Other Noncurrent Assets [Member]
Derivative Assets, Noncurrent, Total	200
Foreign Exchange Contract [Member] \| Other Current Liabilities [Member]
Derivative Liability, Current	3,900
Foreign Exchange Contract [Member] \| Other Noncurrent Liabilities [Member]
Derivative Liability, Noncurrent	$ 5,300
Foreign Exchange Contract [Member] \| Casa Berardi [Member] \| Designated as Hedging Instrument [Member]
Derivative, Number of Instruments Held, Total	140		140	140
Derivative, Notional Amount	$ 239,900		$ 315.1
Foreign Exchange Contract [Member] \| Casa Berardi [Member] \| Designated as Hedging Instrument [Member] \| Minimum [Member]
Derivative, Forward Exchange Rate	1.2702		1.2702	1.2702
Foreign Exchange Contract [Member] \| Casa Berardi [Member] \| Designated as Hedging Instrument [Member] \| Maximum [Member]
Derivative, Forward Exchange Rate	1.3785		1.3785	1.3785
Foreign Exchange Contract [Member] \| San Sebastian [Member] \| Designated as Hedging Instrument [Member]
Derivative, Notional Amount				$ 0
Silver Contracts [Member]
Derivative, Average Price Risk Option Strike Price (in USD per Per Share) \| $ / item					0
Commodity Contract [Member]
Derivative Asset, Total	$ 200
Derivative Liability, Total	500
Commodity Contract [Member] \| Other Current Assets [Member]
Derivative Asset, Current	200
Commodity Contract [Member] \| Other Current Liabilities [Member]
Derivative Liability, Current	9,900
Unsettled Concentrate Sales Contracts [Member]
Derivative, Gain (Loss) on Derivative, Net, Total	(3,300)
Forecasted Future Concentrate Contracts [Member]
Derivative, Gain (Loss) on Derivative, Net, Total	$ 6,100