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Note 3 - Investments (Details Textual) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Equity Securities, FV-NI | $ 15,100 | $ 6,200 |
Equity Securities, FV-NI, Cost | 9,900 | 9,800 |
Available-for-sale Equity Securities, Acquired During Period, Cost Basis | 2,200 | 2,700 |
Marketable Equity Securities Received for Sale of Mineral Interest | 0 | 2,257 | $ 0
Long-term Investments, Total | 15,148 | 6,207 |
Equity Securities, FV-NI, Unrealized Gain (Loss), Total | 10,300 | (2,400) |
Other Assets, Current | 19,114 | $ 12,038 |
Revision of Prior Period, Adjustment [Member] |  |  |
Long-term Investments, Total | (4,200) |  |
Other Assets, Current | $ 4,200 |  |

X
- Definition This item represents the cost of equity securities acquired during the period, which are categorized neither as held-to-maturity nor trading, net of adjustments for other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
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- Definition Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(3)(d)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714 + Details
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