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, 2012
Dec. 31, 2011
Loss Contingencies [Line Items]    
Environmental $ 15.7 $ 15.5
Mine Reclamation and Closing Liability, current and noncurrent 249.4 211.4
Total environmental and mine closure obligations 265.1 226.9
Less current portion 12.3 13.7
Long term environmental and mine closure obligations 252.8 213.2
Previously Owned Or Operating Facilities [Member] | LTV Steel Mining Company [Member]
   
Loss Contingencies [Line Items]    
Mine closure 18.3 16.5
Owned Or Operating Facilities [Member] | U.S. Iron Ore [Member]
   
Loss Contingencies [Line Items]    
Mine closure 81.2 74.3
Owned Or Operating Facilities [Member] | Eastern Canadian Iron Ore [Member]
   
Loss Contingencies [Line Items]    
Mine closure 88.9 68.0
Owned Or Operating Facilities [Member] | Asia Pacific Iron Ore [Member]
   
Loss Contingencies [Line Items]    
Mine closure 22.4 16.3
Owned Or Operating Facilities [Member] | North American Coal [Member]
   
Loss Contingencies [Line Items]    
Mine closure $ 38.6 $ 36.3