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
Mar. 31, 2014
Dec. 31, 2013
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 13,664.6 $ 13,570.9
Allowance for depreciation and depletion (2,578.6) (2,417.5)
Property, plant and equipment, net 11,086.0 11,153.4
Land Rights And Mineral Rights [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 7,841.1 7,819.6
Office And Information Technology [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 126.1 125.7
Buildings [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 269.8 255.2
Mining Equipment [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 1,624.1 1,600.3
Processing Equipment [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 2,199.2 2,148.6
Railroad Equipment [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 315.6 219.0
Electric Power Facilities [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 116.2 114.3
Port Facilities [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 103.2 99.4
Interest Capitalized During Construction [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 23.9 23.8
Land Improvements [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 54.6 69.3
Other [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 94.7 104.4
Construction in Progress [Member]
    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 896.1 $ 991.3