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Environmental Compliance (ARO) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2011
Dec. 31, 2008
Asset Retirement Obligation [Abstract]        
ARO Liability $ 22.6 $ 21.3 $ 22.6 $ 13.7
ARO Asset 19.3 19.3 19.3 13.0
Additional retirement obligation   6.3    
ARO Accretion $ 1.3 $ 1.3