Annual report pursuant to Section 13 and 15(d)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Annual Contributions To The Pension Plans) (Details)

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PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Annual Contributions To The Pension Plans) (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Company contributions $ 3.5 $ 5.5
Expected company contributions, next fiscal year [1] $ 4.1  
Funded percentage 70.00%  
Value of VEBA Trust Assets as a Percentage of the Funding Obligation 0.9  
Pension Benefits [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Company contributions $ 35.7 49.6
Expected company contributions, next fiscal year [1] 1.2  
Direct Payments [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Company contributions 3.5 5.5
Expected company contributions, next fiscal year [1] 4.1  
Veba Trust [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Company contributions 0.0 $ 0.0
Expected company contributions, next fiscal year [1] $ 0.0  
[1] Pursuant to the bargaining agreement, benefits can be paid from VEBA trusts that are at least 70 percent funded (all VEBA trusts are over 70 percent funded at December 31, 2015). Funding obligations have been suspended as Hibbing's, UTAC's, Tilden's and Empire's share of the value of their respective trust assets have reached 90 percent of their obligation.