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