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Note 8 - Commitments, Contingencies, and Obligations (Details Textual) - USD ($) $ in Thousands |  | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Oct. 30, 2019 | Oct. 31, 2019 | Jul. 31, 2018 | Dec. 31, 2014 | Aug. 31, 2012 | Jun. 30, 2011 | Dec. 31, 2014 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Environmental Remediation Expense |  |  |  |  |  |  |  | $ 3,929 | $ 4,690 | $ 6,119
Contractual Obligation, Total |  |  |  |  |  |  |  | 100 |  |
Finance Lease, Liability, Payment, Due, Total |  |  |  |  |  |  |  | 16,819 |  |
Lessee, Operating Lease, Liability, to be Paid, Total |  |  |  |  |  |  |  | 12,622 |  |
Performance Obligation Commitments [Member] |  |  |  |  |  |  |  |  |  |
Surety Bonds |  |  |  |  |  |  |  | 183,000 |  |
Letters of Credit Outstanding, Amount |  |  |  |  |  |  |  | 20,300 |  |
Lucky Friday [Member] |  |  |  |  |  |  |  |  |  |
Open Purchase Orders |  |  |  |  |  |  |  | 4,200 |  |
Casa Berardi [Member] |  |  |  |  |  |  |  |  |  |
Open Purchase Orders |  |  |  |  |  |  |  | 700 |  |
Greens Creek [Member] |  |  |  |  |  |  |  |  |  |
Open Purchase Orders |  |  |  |  |  |  |  | 2,000 |  |
Nevada Operations [Member] |  |  |  |  |  |  |  |  |  |
Open Purchase Orders |  |  |  |  |  |  |  | $ 500 |  |
Canadian Assets of Klondex [Member] |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 13.00% |  |  |  |  |  |  |
PRP Lawsuit in Mineral County, Colorado [Member] |  |  |  |  |  |  |  |  |  |
Loss Contingency, Damages Sought, Value | $ 5,000 |  |  |  |  |  |  |  |  |
Lawsuit filed in Ontario (Canada) Superior Court of Justice [Member] | Waterton Warrants [Member] |  |  |  |  |  |  |  |  |  |
Class of Warrant or Right, Issued During Period, Value |  |  | $ 3,700 |  |  |  |  |  |  |
Class of Warrant or Right, Warrants Entitled, Value |  |  | 8,900 |  |  |  |  |  |  |
Johnny M Mine Area near San Mateo, New Mexico [Member] |  |  |  |  |  |  |  |  |  |
Payment Of Response Costs |  |  |  | $ 1,100 | $ 1,100 |  |  |  |  |
Estimated Response Costs |  |  | $ 9,600 |  |  |  | $ 6,100 |  |  |
Environmental Remediation Expense |  | $ 6,100 |  |  |  |  | $ 5,600 |  |  |
Johnny M Mine Area near San Mateo, New Mexico [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |
Estimated Alternative Response Costs |  |  |  | 0 |  |  |  |  |  |
Johnny M Mine Area near San Mateo, New Mexico [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |
Estimated Alternative Response Costs |  |  |  | $ 221,000 |  |  |  |  |  |
Carpenter Snow Creek Superfund Site, Cascade County, Montana [Member] |  |  |  |  |  |  |  |  |  |
Estimated Response Costs |  |  |  |  |  | $ 4,500 |  |  |  |
Estimated Future Response Cost |  |  |  |  |  | $ 100,000 |  |  |  |

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