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Short-term and Other Investments, Summary (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Other Investments
Gain (loss) during the period	$ (1,093)	$ (1,717)	$ 2,028
Other investments	3,745	3,745		$ 5,462
Midas Gold Shares [Member]
Other Investments
Other investments, unrealized loss	1,093	1,717
Other investments, unrealized gain			$ 2,028
Other investments	$ 3,745	$ 3,745		$ 5,462
Midas Gold Shares held at end of the period	7,802,615	7,802,615		7,802,615

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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