Quarterly report pursuant to Section 13 or 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
Jun. 30, 2013
Dec. 31, 2012
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 13,216.0 $ 13,044.7
Allowance for depreciation and depletion (2,026.4) (1,837.4)
Property, plant and equipment, net 11,189.6 11,207.3
Land Rights And Mineral Rights [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 7,807.6 7,920.8
Office And Information Technology [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 118.8 92.4
Buildings [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 184.9 162.0
Mining Equipment [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 1,401.3 1,290.7
Processing Equipment [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 2,069.5 1,937.4
Railroad Equipment [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 218.9 240.8
Electric Power Facilities [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 62.1 58.7
Port Facilities [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 100.7 114.3
Interest Capitalized During Construction [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 23.1 20.8
Land Improvements [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 60.0 43.9
Other [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 37.5 39.0
Construction in Progress [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 1,131.6 $ 1,123.9