Basis of Preparation of Financial Statements and Nature of Operations (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) property	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Shutdown and care and maintenance costs	$ 350	$ 587
Number of exploration properties | property	10
Velardena properties
Interest acquired (as a percent)	100.00%
Employee severance and other costs			$ 2,000
Shutdown and care and maintenance costs	$ 400
Quarterly holding costs expected with suspended operations	400
Oxide Plant
Expected lease proceeds	$ 4,700