Nature of Operations (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($)
Shutdown and care and maintenance costs	$ 2,016	$ 1,228
Number of exploration properties | property	10
Velardena properties
Interest acquired (as a percent)	100.00%
Employee severance and other costs		$ 1,200
Shutdown and care and maintenance costs	$ 2,000
Quarterly holding costs expected with suspended operations	400
Oxide Plant
Proceeds from lease	$ 4,400