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Note 4 - Environmental and Reclamation Activities - Accrued Reclamation and Closure Cost Liability Activity (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Balance at January 1, 2014 | $ 95,538 | $ 57,250 | $ 105,191
Accruals for estimated costs | 672 | 15,114 | 6,863
Accretion expense | 3,191 | 1,904 | 3,089
Revision of estimated cash flows due to changes in reclamation plans | 2,759 | 4,112 | 675
Payment of reclamation obligations | (17,704) | (1,544) | (58,568)
Balance at December 31, 2014 | 85,580 | 95,538 | $ 57,250
Addition due to development and production at our San Sebastian unit |  | 1,189 |
Revett Mining Company, Inc. [Member] |  |  |
Liability addition due to acquisition of Revett |  | $ 17,513 |
Mines Management [Member] |  |  |
Liability addition due to acquisition of Revett | $ 1,124 |  |

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- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 + Details
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