Basis of Preparation of Financial Statements and Nature of Operations (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2016 USD ($) property	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Shutdown and care and maintenance costs	$ 587
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	$ 600
Quarterly holding costs expected with suspended operations	$ 300
Forecast | Velardena properties
Shutdown and care and maintenance costs		$ 900
Oxide Plant Lease Agreement | Minimum | Forecast | Velardena properties
Proceeds from lease			$ 4,000
Oxide Plant Lease Agreement | Maximum | Forecast | Velardena properties
Proceeds from lease			$ 5,000