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Note 4 - Commitments, Contingencies and Obligations (Details Textual) |  |  |  |  |  | 1 Months Ended | 2 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 26, 2016 | Apr. 15, 2016 USD ($) | Mar. 31, 2016 USD ($) | Dec. 11, 2013 USD ($) | Apr. 12, 2013 USD ($) | Aug. 31, 2012 USD ($) | Jun. 30, 2011 USD ($) | Mar. 01, 2016 USD ($) | Mar. 31, 2016 USD ($) | Jun. 30, 2015 USD ($) | Dec. 31, 2012 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 1980
Joint Venture [Member] | Rio Grande Silver Inc and Emerald Mining and Leasing LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Equity Method Investment, Ownership Percentage |  |  | 70.00% |  |  |  |  |  | 70.00% |  |  |  |
Maximum Environmental Remediation Obligation |  |  |  |  |  |  |  |  | $ 2,500,000 |  |  |  |
Liability for Remediation |  |  |  |  |  |  |  |  | 0 |  |  |  |
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 |  |  |  |  |  |  |  |  | 221,000,000 |  |  |  |
Johnny M Mine Area near San Mateo, New Mexico [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Liability for Remediation |  |  | $ 5,600,000 |  |  |  |  |  |  |  |  |  |
Payment Of Response Costs |  |  |  |  |  | $ 1,100,000 |  |  |  |  | $ 1,100,000 |  |
Estimated Response Costs |  |  |  |  |  |  |  |  | 5,600,000 |  |  |  |
Carpenter Snow Creek Superfund Site, Cascade County, Montana [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated Response Costs |  |  |  |  |  |  | $ 4,500,000 |  |  |  |  |  |
Number of Mining Claims |  |  |  |  |  |  |  |  |  |  |  |  | 6
Estimated Future Response Cost |  |  |  |  |  |  | $ 100,000,000 |  |  |  |  |  |
Gilt Edge Mine Superfund Site [Member] | Costs Incurred by the EPA [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Incurred Response Costs |  |  |  |  |  |  |  |  | 118,000,000 |  |  |  |
Gilt Edge Mine Superfund Site [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Liability for Remediation |  |  |  |  |  |  |  |  | 3,900,000 |  |  |  |
Nelson Tunnel/Commodore Site [Member] | Costs Incurred by the EPA [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Incurred Response Costs |  |  |  |  |  |  |  |  | 10,000,000 |  |  |  |
Nelson Tunnel/Commodore Site [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Liability for Remediation |  |  |  |  |  |  |  |  | 6,000,000 |  |  |  |
Gilt Edge Site and Nelson Tunnel/Commodore Site [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Liability for Remediation |  | $ 9,900,000 |  |  |  |  |  |  |  |  |  |  |
Gilt Edge Site and Nelson Tunnel/Commodore Site [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Liability for Remediation |  |  |  |  |  |  |  |  |  | $ 9,900,000 |  |  |
Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Days for Public Comment | 30 days |  |  |  |  |  |  |  |  |  |  |  |
Uncooperative Insurer [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Lawsuit Against Uncooperative Insurer |  |  |  |  |  |  |  |  | 700,000 |  |  |  |
Insurance Companies and Another PRP [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Remaining Liability For Redemption |  |  |  |  |  |  |  |  | 6,400,000 |  |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Issuance of Debt |  |  |  |  | $ 500,000,000 |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  | 6.875% |  |  |  |  |  |  |  |
Debt Instrument, Increase (Decrease), Net |  |  |  |  |  |  |  |  |  |  |  | $ 6,500,000 |
Lucky Friday [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Open Purchase Orders |  |  | 1,000,000 |  |  |  |  |  | 1,000,000 |  |  |  |
Noncapital Costs |  |  |  |  |  |  |  | $ 500,000 |  |  |  |  |
Casa Berardi [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Open Purchase Orders |  |  | 700,000 |  |  |  |  |  | 700,000 |  |  |  |
Noncapital Costs |  |  |  |  |  |  |  | 3,600,000 |  |  |  |  |
Greens Creek [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Open Purchase Orders |  |  | 600,000 |  |  |  |  |  | 600,000 |  |  |  |
Noncapital Costs |  |  |  |  |  |  |  | 2,400,000 |  |  |  |  |
Revett Mining Company, Inc. [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Held for Reclamation |  |  | 6,500,000 |  |  |  |  |  | 6,500,000 |  |  |  |
Contractual Obligations |  |  | 11,700,000 |  |  |  |  |  | 11,700,000 |  |  |  |
Commitments For Capital Lease Payments |  |  |  |  |  |  |  | $ 16,300,000 |  |  |  |  |
Surety Bonds |  |  | $ 100,500,000 |  |  |  |  |  | $ 100,500,000 |  |  |  |
Loss Contingency, Number of Plaintiffs |  |  |  | 4 |  |  |  |  |  |  |  |  |
Loss Contingency, Estimate of Possible Loss |  |  |  | $ 1,000,000 |  |  |  |  |  |  |  |  |

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