Quarterly report pursuant to Section 13 or 15(d)

Basis Of Presentation And Significant Accounting Policies (Investments In Unconsolidated Ventures) (Details)

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Basis Of Presentation And Significant Accounting Policies (Investments In Unconsolidated Ventures) (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2012
Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]    
Investment $ 512.6 $ 504.8
Amapa [Member] | Investments In Ventures [Member]
   
Schedule of Equity Method Investments [Line Items]    
Interest Percentage 30.00%  
Investment 492.5 498.6
AusQuest [Member] | Investments In Ventures [Member]
   
Schedule of Equity Method Investments [Line Items]    
Interest Percentage 30.00%  
Investment 3.5 3.7
Cockatoo [Member] | Other Liabilities [Member]
   
Schedule of Equity Method Investments [Line Items]    
Interest Percentage 50.00%  
Investment (13.9) (15.0)
Hibbing [Member] | Other Liabilities [Member]
   
Schedule of Equity Method Investments [Line Items]    
Interest Percentage 23.00%  
Investment (4.4) (6.8)
Other Equity Investees [Member] | Investments In Ventures [Member]
   
Schedule of Equity Method Investments [Line Items]    
Investment $ 34.9 $ 24.3