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Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.6
Basis Of Presentation And Significant Accounting Policies (Investments In Unconsolidated Ventures) (Detail) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Schedule of Equity Method Investments [Line Items] Ìý Ìý
Investment $ 508.7 $ 504.8
Amapa [Member] | Investments In Ventures [Member]
Ìý Ìý
Schedule of Equity Method Investments [Line Items] Ìý Ìý
Investment 493.4 498.6
Interest Percentage 30.00% Ìý
Cockatoo [Member] | Other Liabilities [Member]
Ìý Ìý
Schedule of Equity Method Investments [Line Items] Ìý Ìý
Investment (16.7) (15.0)
Interest Percentage 50.00% Ìý
Hibbing [Member] | Other Liabilities [Member]
Ìý Ìý
Schedule of Equity Method Investments [Line Items] Ìý Ìý
Investment (5.8) (6.8)
Interest Percentage 23.00% Ìý
Other Equity Investees [Member] | Investments In Ventures [Member]
Ìý Ìý
Schedule of Equity Method Investments [Line Items] Ìý Ìý
Investment $ 37.8 $ 28.0