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Note 12 - Fair Value Measurement (Tables) | 3 Months Ended
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Mar. 31, 2015
Fair Value Disclosures [Abstract] |
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] |
Description |  | Balance at March 31, 2015 |  |  | Balance at December 31, 2014 |  |  | Input Hierarchy Level |
Assets: |  |  |  |  |  |  |  |  |  |  |  |
Cash and cash equivalents: |  |  |  |  |  |  |  |  |  |  |  |
Money market funds and other bank deposits |  | $ | 196,231 |  |  | $ | 209,665 |  |  | Level 1 |
Available for sale securities: |  |  |  |  |  |  |  |  |  |  |  |
Equity securities – mining industry |  |  | 4,334 |  |  |  | 4,920 |  |  | Level 1 |
Trade accounts receivable: |  |  |  |  |  |  |  |  |  |  |  |
Receivables from provisional concentrate sales |  |  | 27,280 |  |  |  | 17,696 |  |  | Level 2 |
Restricted cash balances: |  |  |  |  |  |  |  |  |  |  |  |
Certificates of deposit and other bank deposits |  |  | 883 |  |  |  | 883 |  |  | Level 1 |
Derivative contracts: |  |  |  |  |  |  |  |  |  |  |  |
Metal forward contracts |  |  | 14,317 |  |  |  | 11,347 |  |  | Level 2 |
Total assets |  | $ | 243,045 |  |  | $ | 244,511 |  |  |  |  |

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- Definition Tabular disclosure of assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19190-110258 + Details
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