Quarterly report pursuant to Section 13 or 15(d)

INVENTORIES (Narrative) (Details)

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INVENTORIES (Narrative) (Details) (Cost of Sales [Member], USD $)
In Millions, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Eastern Canadian Iron Ore [Member]
        
Inventory [Line Items]        
Inventory Write-down $ 2.6   $ 18.6  
North American Coal [Member]
        
Inventory [Line Items]        
Inventory Write-down 5.0 2.6 42.1 5.3
Bloom Lake [Member] | Eastern Canadian Iron Ore [Member]
        
Inventory [Line Items]        
Inventory Write-down 1.9      
Wabush [Member] | Eastern Canadian Iron Ore [Member]
        
Inventory [Line Items]        
Inventory Write-down 0.7      
Pellets [Member] | Wabush [Member]
        
Inventory [Line Items]        
Inventory Write-down       11.1
Unsaleable Inventory Impairment Charge       10.6
Sinter feed [Member] | Eastern Canadian Iron Ore [Member]
        
Inventory [Line Items]        
Inventory Write-down   $ 5.9   $ 10.6