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
Sep. 30, 2015
Dec. 31, 2014
Inventory, Net [Abstract]    
Finished Goods $ 278.8 $ 158.5
Work-in Process 72.9 101.6
Total Inventory 351.7 260.1
U.S. Iron Ore [Member]    
Inventory, Net [Abstract]    
Finished Goods 260.3 132.1
Work-in Process 23.3 13.5
Total Inventory 283.6 145.6
Asia Pacific Iron Ore [Member]    
Inventory [Line Items]    
Other Inventory, Noncurrent 12.0 0.0
Inventory, Net [Abstract]    
Finished Goods 18.5 26.4
Work-in Process 49.6 88.1
Total Inventory $ 68.1 $ 114.5