Annual report pursuant to Section 13 and 15(d)

Environmental And Mine Closure Obligations (Schedule Of Environmental Loss Contingencies By Site) (Details)

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Environmental And Mine Closure Obligations (Schedule Of Environmental Loss Contingencies By Site) (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Loss Contingencies [Line Items]    
Environmental $ 15.5 $ 13.7
Total environmental and mine closure obligations 235.7 199.1
Less current portion 13.7 14.2
Mine closure obligation 220.2 185.4
Long term environmental and mine closure obligations 222.0 184.9
Previously Owned Or Operating Facilities [Member] | L T V Steel Mining Company [Member]
   
Loss Contingencies [Line Items]    
Mine closure obligation 16.5 17.1
Owned Or Operating Facilities [Member] | U.S. Iron Ore [Member]
   
Loss Contingencies [Line Items]    
Mine closure obligation 74.3 62.7
Owned Or Operating Facilities [Member] | Eastern Canadian Iron Ore [Member]
   
Loss Contingencies [Line Items]    
Mine closure obligation 68.0 49.3
Owned Or Operating Facilities [Member] | North American Coal [Member]
   
Loss Contingencies [Line Items]    
Mine closure obligation 36.3 34.7
Owned Or Operating Facilities [Member] | Asia Pacific Iron Ore [Member]
   
Loss Contingencies [Line Items]    
Mine closure obligation 16.3 15.4
Owned Or Operating Facilities [Member] | Other Regions [Member]
   
Loss Contingencies [Line Items]    
Mine closure obligation $ 8.8 $ 6.2