Other Investments, Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	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