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Reclamation (Details) (USD $)
3 Months Ended
Mar. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Asset retirement obligation      
Asset retirement obligation - Beginning $ 57,454,000   $ 34,457,000
Accretion 1,317,000 3,442,000  
Addition and changes in estimates 0 20,236,000  
Settlements (311,000) (681,000)  
Asset retirement obligation - December 31 58,460,000 57,454,000 34,457,000
Reclamation and Mine Closure (Textual) [Abstract]      
Accrued reclamation liabilities $ 900,000 $ 1,000,000