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, 2018
Jan. 01, 2018
Dec. 31, 2017
Inventory, Net [Abstract]      
Finished Goods $ 287.4   $ 160.4
Work-in Process 37.0   23.0
Total Inventory 324.4 $ 132.0 183.4
U.S. Iron Ore [Member]      
Inventory, Net [Abstract]      
Finished Goods 267.2   127.1
Work-in Process 36.0   11.3
Total Inventory 303.2   138.4
Asia Pacific Iron Ore [Member]      
Inventory, Net [Abstract]      
Finished Goods 20.2   33.3
Work-in Process 1.0   11.7
Total Inventory $ 21.2   $ 45.0