Annual report pursuant to Section 13 and 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
Dec. 31, 2013
Dec. 31, 2012
Loss Contingencies [Line Items]    
Environmental $ 8.4 $ 15.7
Mine Reclamation and Closing Liability, current and noncurrent 312.6 249.4
Total environmental and mine closure obligations 321.0 265.1
Less current portion 11.3 12.3
Long term environmental and mine closure obligations 309.7 252.8
U.S. Iron Ore [Member] | Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent 152.2 81.2
Eastern Canadian Iron Ore [Member] | Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent 78.2 88.9
Asia Pacific Iron Ore [Member] | Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent 25.5 22.4
North American Coal [Member] | Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent 34.7 38.6
LTV Steel Mining Company [Member] | Previously Owned Or Operating Facilities [Member]
    
Loss Contingencies [Line Items]    
Mine Reclamation and Closing Liability, current and noncurrent $ 22.0 $ 18.3