Annual report pursuant to Section 13 and 15(d)

RELATED PARTIES (Narrative) (Details)

v3.10.0.1
RELATED PARTIES (Narrative) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2018
USD ($)
Facility
Dec. 31, 2017
USD ($)
installment
Segment Reporting Information [Line Items]    
Noncontrolling Interest, Ownership Percentage by Parent 100.00%  
Due to Related Parties, Current $ 1.8 $ 12.3
Acquisition of Noncontrolling Interest   $ (105.0)
Mining and Pelletizing [Member]    
Segment Reporting Information [Line Items]    
Number Of Mines | Facility 4  
Joint Venture Partners [Member] | Mining and Pelletizing [Member]    
Segment Reporting Information [Line Items]    
Number Of Mines | Facility 1  
Empire [Member]    
Segment Reporting Information [Line Items]    
Noncontrolling Interest, Ownership Percentage by Parent   100.00%
Increase in Ownership Equity   21.00%
Distribution of Noncontrolling Interest   $ 132.7
Noncontrolling Interest Purchase, Number Of Installment Payments | installment   3
Stockholders' Equity, Period Increase (Decrease)   $ (12.1)
Acquisition of Noncontrolling Interest   $ (116.7)
Other Liabilities [Member] | Empire [Member]    
Segment Reporting Information [Line Items]    
Noncontrolling Interest Purchase, Installment Amount $ 44.2  
Other Noncurrent Liabilities [Member] | Empire [Member]    
Segment Reporting Information [Line Items]    
Noncontrolling Interest Purchase, Installment Amount $ 44.2