Annual report pursuant to Section 13 and 15(d)

PROPERTY, PLANT AND EQUIPMENT (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Details)

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PROPERTY, PLANT AND EQUIPMENT (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross $ 13,044.7 $ 11,695.6  
Allowance for depreciation and depletion (1,837.4) (1,291.5)  
Property, plant and equipment, net 11,207.3 10,404.1 3,979.2
Land Rights And Mineral Rights [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 7,920.8 7,868.7  
Office And Information Technology [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 92.4 66.8  
Buildings [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 162.0 132.2  
Mining Equipment [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 1,290.7 1,323.8  
Processing Equipment [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 1,937.4 1,311.6  
Railroad Equipment [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 240.8 161.6  
Electric Power Facilities [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 58.7 57.9  
Port Facilities [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 114.3 64.1  
Interest Capitalized During Construction [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 20.8 22.5  
Land Improvements [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 43.9 30.4  
Other [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 39.0 43.2  
Construction in Progress [Member]
     
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross $ 1,123.9 $ 612.8