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BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Investments In Unconsolidated Ventures) (Details) (USD $)
In Millions, unless otherwise specified |
Sep. 30, 2013
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Dec. 31, 2012
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| Schedule of Equity Method Investments [Line Items] | ||||||||
| Investment | $ 71.5 | $ 108.4 | ||||||
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Investments in Ventures [Member] | Amapa [Member]
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| Schedule of Equity Method Investments [Line Items] | ||||||||
| Ownership interest, equity method investment | 30.00% | |||||||
| Total percentage of Amapa sold | 100.00% | |||||||
| Investment | 29.4 | 101.9 | ||||||
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Investments in Ventures [Member] | Hibbing [Member]
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| Schedule of Equity Method Investments [Line Items] | ||||||||
| Ownership interest, equity method investment | 23.00% | [1] | ||||||
| Investment | 8.3 | [1] | ||||||
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Investments in Ventures [Member] | Other Equity Investees [Member]
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| Schedule of Equity Method Investments [Line Items] | ||||||||
| Investment | 33.8 | 33.9 | ||||||
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Other Noncurrent Liabilities [Member] | Cockatoo [Member]
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| Schedule of Equity Method Investments [Line Items] | ||||||||
| Ownership interest, equity method investment | 0.00% | [2] | 50.00% | [2] | ||||
| Investment | (25.3) | [2] | ||||||
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Other Noncurrent Liabilities [Member] | Hibbing [Member]
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| Schedule of Equity Method Investments [Line Items] | ||||||||
| Investment | $ (2.1) | [1] | ||||||
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