Annual report pursuant to Section 13 and 15(d)

RELATED PARTIES (Narrative) (Details)

v3.3.1.900
RELATED PARTIES (Narrative) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2015
USD ($)
Facility
Dec. 31, 2014
USD ($)
Segment Reporting Information [Line Items]    
Due from Related Parties, Current $ 15.8 $ 127.6
Due to Related Parties, Current $ 14.5 $ 11.8
U.S. Iron Ore [Member]    
Segment Reporting Information [Line Items]    
Number Of Mines | Facility 5  
Joint Venture Partners [Member] | U.S. Iron Ore [Member]    
Segment Reporting Information [Line Items]    
Number Of Mines | Facility 3  
Empire [Member] | Arcelor Mittal [Member]    
Segment Reporting Information [Line Items]    
Recorded Distributions of Partners' Equity Amounts $ 51.7  
Paid Distributions of Partners' Equity Amounts $ 40.6