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Summary of Significant Accounting Policies (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Nature of Operations    
Ownership percentage of subsidiaries 100.00%  
Revenue Recognition    
Number of days used for observing average prices of metals 10 days  
Inventories    
Metals inventory $ 0 $ 477
Buildings | Minimum    
Property, plant and equipment and long-lived asset impairment    
Useful life 30 years  
Buildings | Maximum    
Property, plant and equipment and long-lived asset impairment    
Useful life 40 years  
Mining equipment and machinery | Minimum    
Property, plant and equipment and long-lived asset impairment    
Useful life 3 years  
Mining equipment and machinery | Maximum    
Property, plant and equipment and long-lived asset impairment    
Useful life 8 years  
Other furniture and equipment | Minimum    
Property, plant and equipment and long-lived asset impairment    
Useful life 3 years  
Other furniture and equipment | Maximum    
Property, plant and equipment and long-lived asset impairment    
Useful life 5 years