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) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Company contributions $ 39.0 $ 37.4
Expected company contributions, next fiscal year 22.4 [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 67.7 70.1
Expected company contributions, next fiscal year 51.8 [1]  
Veba Trust [Member]
   
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Company contributions 17.4 17.4
Expected company contributions, next fiscal year 14.1 [1]  
Direct Payments [Member]
   
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Company contributions 21.6 20.0
Expected company contributions, next fiscal year $ 8.3 [1]  
[1] Pursuant to the bargaining agreement, benefits can be paid from VEBA trusts that are at least 70 percent funded (all VEBA trusts are 70 percent funded at December 31, 2012). Funding obligations are suspended when Hibbing's, UTAC's, Tilden's and Empire's share of the value of their respective trust assets reaches 90 percent of their obligation.