Quarterly report pursuant to Section 13 or 15(d)

Inventories (Schedule Of Inventories) (Details)

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Inventories (Schedule Of Inventories) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2012
Dec. 31, 2011
Finished Goods $ 490.4 $ 291.3
Work-in Process 205.5 184.4
Total Inventory 695.9 475.7
U.S. Iron Ore [Member]
    
Finished Goods 250.0 100.2
Work-in Process 25.0 8.5
Total Inventory 275.0 108.7
Eastern Canadian Iron Ore [Member]
    
Finished Goods 133.6 96.2
Work-in Process 45.0 43.0
Total Inventory 178.6 139.2
North American Coal [Member]
    
Finished Goods 48.0 19.7
Work-in Process 115.1 110.5
Total Inventory 163.1 130.2
Asia Pacific Iron Ore [Member]
    
Finished Goods 41.6 57.2
Work-in Process 19.1 21.6
Total Inventory 60.7 78.8
Other Segment [Member]
    
Finished Goods 17.2 18.0
Work-in Process 1.3 0.8
Total Inventory $ 18.5 $ 18.8