Annual report pursuant to Section 13 and 15(d)

BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Investments In Unconsolidated Ventures) (Details)

v2.4.0.6
BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Investments In Unconsolidated Ventures) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 27, 2012
Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]      
Investment $ 108.4   $ 504.8
Amapa [Member] | Investments In Ventures [Member]
     
Schedule of Equity Method Investments [Line Items]      
Interest Percentage   30.00%  
Total percentage of Amapa sold 100.00%    
Investment 101.9   498.6
Impairment of equity method investment 365.4    
Cockatoo [Member] | Other Liabilities [Member]
     
Schedule of Equity Method Investments [Line Items]      
Interest Percentage 50.00%    
Investment (25.3)   (15.0)
Hibbing [Member] | Other Liabilities [Member]
     
Schedule of Equity Method Investments [Line Items]      
Investment (2.1)   (6.8)
Other Equity Investees [Member] | Investments In Ventures [Member]
     
Schedule of Equity Method Investments [Line Items]      
Investment $ 33.9   $ 28.0
Hibbing [Member] | Hibbing [Member] | Investments In Ventures [Member]
     
Schedule of Equity Method Investments [Line Items]      
Interest Percentage 23.00%    
Latin American Iron Ore [Member] | Amapa [Member]
     
Schedule of Equity Method Investments [Line Items]      
Interest Percentage 30.00%