Quarterly report [Sections 13 or 15(d)]

Mineral Properties - Additional Disclosure (Details)

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Mineral Properties - Additional Disclosure (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2013
Dec. 31, 2005
Nfu wyoming Llc    
Mineral Properties    
Percentage Of Asset Acquired   100.00%
Aggregate Consideration   $ 20.0
Pathfinder properties    
Mineral Properties    
Percentage Of Asset Acquired 100.00%  
Aggregate Consideration $ 6.7  
Estimated Asset Reclamation Obligation $ 5.7