Quarterly report pursuant to Section 13 or 15(d)

Environmental And Mine Closure Obligations (Narrative) (Details)

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Environmental And Mine Closure Obligations (Narrative) (Details) (USD $)
In Millions
Sep. 30, 2011
Dec. 31, 2010
Environmental And Mine Closure Obligations [Abstract]    
Environmental and mine closure liabilities $ 225.2 $ 199.1