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Reclamation and Mine Closure (Details) (USD $)
3 Months Ended 15 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Asset retirement obligation      
Asset retirement obligation - Beginning     $ 32,714,000
Accretion 3,442,000 2,911,000  
Addition and changes in estimates 20,236,000 (1,073,000)  
Settlements (681,000) (95,000)  
Asset retirement obligation - December 31 57,454,000 34,457,000 32,714,000
Reclamation and Mine Closure (Textual) [Abstract]      
Accrued reclamation liabilities $ 1,000,000 $ 900,000