Quarterly report pursuant to Section 13 or 15(d)

RELATED PARTIES (Narrative) (Details)

v2.4.0.8
RELATED PARTIES (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2014
Dec. 31, 2013
Segment Reporting Information [Line Items]    
Extension of ArcelorMittal Contract 2 years  
Due from Related Parties, Current $ 103.4 $ 132.0
Due to Related Parties, Current $ 27.2 $ 25.1
U.S. Iron Ore [Member]
   
Segment Reporting Information [Line Items]    
Number of mines (in number of facilities) 5  
Eastern Canadian Iron Ore [Member]
   
Segment Reporting Information [Line Items]    
Number of mines (in number of facilities) 2  
Joint Venture Partners [Member] | U.S. Iron Ore [Member]
   
Segment Reporting Information [Line Items]    
Number of mines (in number of facilities) 3  
Joint Venture Partners [Member] | Eastern Canadian Iron Ore [Member]
   
Segment Reporting Information [Line Items]    
Number of mines (in number of facilities) 1