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           Asset Retirement and Reclamation Obligations 
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        12 Months Ended | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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           Dec. 31, 2013 
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| Asset Retirement Obligation Disclosure [Abstract] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Asset Retirement and Reclamation Obligations |               
 
  Asset retirement obligations ("ARO")  for the Lost Creek Project are equal to the present value of all  estimated future costs required to remediate any environmental  disturbances that exist as of the end of the period, using discount  rates    ranging from   0.3% to   3.8%. Included in this liability are the costs of  closure, reclamation, demolition and stabilization of the mines,  processing plants, infrastructure, aquifer restoration, waste dumps  and ongoing post-closure environmental monitoring and maintenance  costs. At December 31, 2013, the total undiscounted amount of the  future cash needs was estimated to be $17.7  million. The schedule of payments required to settle the ARO  liability extends through 2033.
     The restricted cash as discussed in note 8 is related to  surety bonds and letters of credit which provide security to the  related governmental agencies on these obligations.     
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