Quarterly report pursuant to Section 13 or 15(d)

RELATED PARTIES (Narrative) (Details)

v2.4.0.6
RELATED PARTIES (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Dec. 31, 2012
Mar. 31, 2013
U.S. Iron Ore [Member]
Facility
Mar. 31, 2013
Eastern Canadian Iron Ore [Member]
Facility
Mar. 31, 2013
Joint Venture Partners [Member]
U.S. Iron Ore [Member]
Facility
Mar. 31, 2013
Joint Venture Partners [Member]
Eastern Canadian Iron Ore [Member]
Facility
Segment Reporting Information [Line Items]            
Number of mines (in number of facilities)     5 2 3 1
Accounts receivable and derivative assets related parties $ 119.6 $ 149.8        
Other current liabilities related parties $ 0 $ 20.2