PROPERTY, PLANT AND EQUIPMENT (Value Of Each Of The Major Classes Of Consolidated Depreciable Assets) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 13,710.0	$ 13,570.9
Allowance for depreciation and depletion	(2,705.2)	(2,417.5)
Property, plant and equipment, net	11,004.8	11,153.4
Land Rights And Mineral Rights [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	7,854.2	7,819.6
Office And Information Technology [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	125.8	125.7
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	307.1	255.2
Mining Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,199.3	1,819.3
Processing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,943.9	2,148.6
Electric Power Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	114.6	114.3
Port Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	105.1	99.4
Interest Capitalized During Construction [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	23.1	23.8
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	54.5	69.3
Other [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	89.6	104.4
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 892.8	$ 991.3