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Other Investments, Summary (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Other Investments |  |
Fair value at beginning of period | $ 3,746 |
Gain (loss) during the period | 1,716 | $ (1,248)
Fair value at end of period | 5,462 | 3,746
Midas Gold Shares |  |
Other Investments |  |
Fair value at beginning of period | 3,746 | 4,994
Gain (loss) during the period | 1,716 | (1,248)
Fair value at end of period | $ 5,462 | $ 3,746
Midas Gold Shares held at end of the period | 7,802,615 | 7,802,615

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