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Note 5 - Environmental and Reclamation Activities (Details Textual) $ in Thousands, $ in Millions | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2020 CAD ($) | Jun. 30, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2019 CAD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Accrual for Environmental Loss Contingencies, Ending Balance | $ 116,048 |  |  | $ 108,374 |  | $ 116,048 | $ 108,389 | $ 86,045
Asset Retirement Obligation, Liabilities Incurred | 1,500 |  |  |  |  |  |  |
Casa Berardi [Member] |  |  |  |  |  |  |  |
Asset Retirement Obligation, Revision of Estimate Before Discounting |  | $ 29.1 |  |  | $ 15.7 |  |  |
Asset Retirement Obligation, Liabilities Incurred | 6,700 |  |  |  |  |  |  |
Lucky Friday [Member] |  |  |  |  |  |  |  |
Asset Retirement Obligation, Revision of Estimate Before Discounting | 36,900 |  |  | 34,300 |  |  |  |
San Sebastian [Member] |  |  |  |  |  |  |  |
Asset Retirement Obligation, Revision of Estimate Before Discounting | 600 |  |  |  |  |  |  |
Asset Retirement Obligation, Liabilities Incurred | $ 600 |  |  |  |  |  |  |
Greens Creek [Member] |  |  |  |  |  |  |  |
Asset Retirement Obligation, Revision of Estimate Before Discounting |  |  | $ 107,700 | $ 114,900 |  |  |  |
Asset Retirement Obligation, Liabilities Incurred |  |  | $ 5,100 |  |  |  |  |
Minimum [Member] |  |  |  |  |  |  |  |
Inflation Rate, Asset Retirement Obligation |  |  |  |  |  | 2.00% |  |
Minimum [Member] | Reclamation and Abandonment Costs [Member] | Measurement Input, Risk Free Interest Rate [Member] |  |  |  |  |  |  |  |
Derivative Liability, Measurement Input | 0.0575 |  |  |  |  | 0.0575 |  |
Minimum [Member] | Asset Retirement Obligation [Member] | Measurement Input, Risk Free Interest Rate [Member] |  |  |  |  |  |  |  |
Derivative Liability, Measurement Input | 0.0275 |  |  |  |  | 0.0275 |  |
Maximum [Member] |  |  |  |  |  |  |  |
Inflation Rate, Asset Retirement Obligation |  |  |  |  |  | 4.00% |  |
Maximum [Member] | Reclamation and Abandonment Costs [Member] | Measurement Input, Risk Free Interest Rate [Member] |  |  |  |  |  |  |  |
Derivative Liability, Measurement Input | 0.145 |  |  |  |  | 0.145 |  |
Maximum [Member] | Asset Retirement Obligation [Member] | Measurement Input, Risk Free Interest Rate [Member] |  |  |  |  |  |  |  |
Derivative Liability, Measurement Input | 0.075 |  |  |  |  | 0.075 |  |

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- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 + Details
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