Property, Plant and Equipment - Impairments (Details) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($) ha	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) ha item
Property, plant and equipment
Impairment Charges				$ 13,181
Proceeds from sale of assets				789	$ 982
Gain on sale of assets				719	689
Property, plant and equipment, gross				35,849	50,255
Zacatecas District
Property, plant and equipment
Proceeds from sale of assets					700
Gain on sale of assets					$ 500
Number of Mining Concessions Sold | item					45
Area in Hectares | ha					770
Velardena properties
Property, plant and equipment
Impairment Charges	$ 13,181				$ 0
Property, plant and equipment, gross	36,057		$ 36,057
Peruvian Exploration Properties
Property, plant and equipment
Proceeds from sale of assets				300	200
Area in Hectares | ha		1,100
Amount of Agreement to Sell Property		$ 500
Prior to impairment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	49,238		49,238
Impairment adjustment | Velardena properties
Property, plant and equipment
Impairment Charges			13,181
Mineral properties
Property, plant and equipment
Property, plant and equipment, gross				9,630	22,397
Mineral properties | Velardena properties
Property, plant and equipment
Impairment Charges			13,200
Property, plant and equipment, gross	9,630		9,630
Mineral properties | Prior to impairment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	21,936		21,936
Mineral properties | Impairment adjustment | Velardena properties
Property, plant and equipment
Impairment Charges			12,306
Exploration properties
Property, plant and equipment
Property, plant and equipment, gross				2,518	2,743
Exploration properties | Velardena properties
Property, plant and equipment
Impairment Charges	458
Property, plant and equipment, gross	2,543		2,543
Exploration properties | Prior to impairment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	3,001		3,001
Exploration properties | Impairment adjustment | Velardena properties
Property, plant and equipment
Impairment Charges			458
Royalty properties
Property, plant and equipment
Property, plant and equipment, gross				200	200
Royalty properties | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	200		200
Royalty properties | Prior to impairment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	200		200
Buildings
Property, plant and equipment
Property, plant and equipment, gross				4,377	4,377
Buildings | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	4,377		4,377
Buildings | Prior to impairment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	4,377		4,377
Mining equipment and machinery
Property, plant and equipment
Property, plant and equipment, gross				16,998	17,695
Mining equipment and machinery | Argentina
Property, plant and equipment
Proceeds from sale of assets				100
Mining equipment and machinery | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	17,181		17,181
Mining equipment and machinery | Peruvian Exploration Properties
Property, plant and equipment
Proceeds from sale of assets				500
Gain on sale of assets				200
Mining equipment and machinery | Prior to impairment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	17,181		17,181
Other furniture and equipment
Property, plant and equipment
Property, plant and equipment, gross				841	841
Other furniture and equipment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	841		841
Other furniture and equipment | Prior to impairment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	841		841
Asset retirement cost
Property, plant and equipment
Impairment Charges	417
Property, plant and equipment, gross				$ 1,285	$ 2,002
Asset retirement cost | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	1,285		1,285
Asset retirement cost | Prior to impairment | Velardena properties
Property, plant and equipment
Property, plant and equipment, gross	$ 1,702		1,702
Asset retirement cost | Impairment adjustment | Velardena properties
Property, plant and equipment
Impairment Charges			417
Mineral and exploration properties | Velardena properties
Property, plant and equipment
Impairment Charges			$ 12,800