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
Mar. 31, 2017
Dec. 31, 2016
Inventory, Net [Abstract]    
Finished Goods $ 209.2 $ 148.0
Work-in Process 41.6 30.4
Total Inventory 250.8 178.4
U.S. Iron Ore [Member]    
Inventory, Net [Abstract]    
Finished Goods 194.6 124.4
Work-in Process 26.3 12.6
Total Inventory 220.9 137.0
Asia Pacific Iron Ore [Member]    
Inventory, Net [Abstract]    
Finished Goods 14.6 23.6
Work-in Process 15.3 17.8
Total Inventory $ 29.9 $ 41.4