Quarterly report pursuant to Section 13 or 15(d)

Mineral Properties (Details Textual)

v2.4.0.8
Mineral Properties (Details Textual) (USD $)
In Millions, unless otherwise specified
 6 Months Ended
Jun. 30, 2014
Mineral Properties [Line Items]  
Percentage Of Production Royalty On Acquisition 5.00%
Assumption Amount In Estimated Asset Reclamation Obligation $ 5.7
Allocated To Mineral Properties [Member]
  
Mineral Properties [Line Items]  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities 15.3
Deferred Tax Liabilites [Member]
  
Mineral Properties [Line Items]  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities 3.3
Asset Retirement Obligation [Member]
  
Mineral Properties [Line Items]  
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities 5.7
Pathfinder Mines Corporation [Member]
  
Mineral Properties [Line Items]  
Payments to Acquire Businesses, Gross 6.7
Nfu Wyoming Llc [Member]
  
Mineral Properties [Line Items]  
Percentage of asset acquired 100.00%
Purchased property interest $ 20