Quarterly report pursuant to Section 13 or 15(d)

ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details)

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ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2014
Dec. 31, 2013
Loss Contingencies [Line Items]    
Environmental $ 11.0 $ 8.4
Mine Reclamation and Closing Liability, current and noncurrent 299.3 312.6
Total environmental and mine closure obligations 310.3 321.0
Less current portion 5.6 11.3
Long term environmental and mine closure obligations 304.7 309.7
U.S. Iron Ore [Member] | Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent 137.5 152.2
Eastern Canadian Iron Ore [Member] | Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent 76.3 78.2
Asia Pacific Iron Ore [Member] | Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent 27.4 25.5
North American Coal [Member] | Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent 35.7 34.7
LTV Steel Mining Company [Member] | Previously Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent $ 22.4 $ 22.0