Impairment of Long Lived Assets (Details) $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Jun. 30, 2013 USD ($)
Impairment of Long Lived Assets
Net deferred tax asset (liability)			$ 0	$ 0
Details of components of the impairment of long lived assets
Impairment Charges			$ 13,181
Mineral and exploration properties
Details of components of the impairment of long lived assets
Net Book Value					$ 6,000
Buildings, plant and equipment
Details of components of the impairment of long lived assets
Net Book Value After Impairment	$ 3,236	$ 3,236
Buildings, plant and equipment | Prior to impairment
Details of components of the impairment of long lived assets
Net Book Value After Impairment	3,236	3,236
Asset retirement cost
Details of components of the impairment of long lived assets
Impairment Charges	417
Asset retirement cost | Prior to impairment
Details of components of the impairment of long lived assets
Net Book Value After Impairment	417	417
Velardena properties
Impairment of Long Lived Assets
Number of asset groups | item			2
Details of components of the impairment of long lived assets
Impairment Charges	13,181			$ 0
Net Book Value After Impairment	3,718	3,718
Velardena properties | Prior to impairment
Details of components of the impairment of long lived assets
Net Book Value After Impairment	16,899	16,899
Velardena properties | Impairment adjustment
Details of components of the impairment of long lived assets
Impairment Charges		13,181
Velardena properties | Mineral and exploration properties
Details of components of the impairment of long lived assets
Impairment Charges	12,306
Net Book Value After Impairment	1,354	1,354
Velardena properties | Mineral and exploration properties | Prior to impairment
Details of components of the impairment of long lived assets
Net Book Value After Impairment	13,660	13,660
Velardena properties | Exploration properties
Details of components of the impairment of long lived assets
Impairment Charges	458
Velardena properties | Exploration properties | Prior to impairment
Details of components of the impairment of long lived assets
Net Book Value After Impairment	458	458
Velardena properties | Exploration properties | Impairment adjustment
Details of components of the impairment of long lived assets
Impairment Charges		458
Velardena properties | Asset retirement cost | Impairment adjustment
Details of components of the impairment of long lived assets
Impairment Charges		417
Velardena properties | Other working capital, net
Details of components of the impairment of long lived assets
Net Book Value After Impairment	(872)	(872)
Velardena properties | Other working capital, net | Prior to impairment
Details of components of the impairment of long lived assets
Net Book Value After Impairment	(872)	(872)
Velardena properties | Materials and supplies inventory
Impairment of Long Lived Assets
Obsolescence charge reflected in shutdown costs			$ 300
Velardena properties | Mineral Properties Asset Group | Sales of similar properties
Details of components of the impairment of long lived assets
Net Book Value	1,400	1,400
Velardena properties | Mineral Properties Asset Group | Materials and supplies inventory
Impairment of Long Lived Assets
Obsolescence charge reflected in shutdown costs		400
Reduction in reserve for obsolescence.			$ 100
Velardena properties | Oxide Plant Asset Group
Details of components of the impairment of long lived assets
Net Book Value	$ 1,300	$ 1,300