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Related Parties (Summary Of Other Ownership Interests) (Details)
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Mar. 31, 2012
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Mar. 31, 2011
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|---|---|---|
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Empire [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 79.00% | 79.00% |
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Tilden [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 85.00% | 85.00% |
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Bloom Lake [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 75.00% | 75.00% |
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Cliffs Natural Resources [Member] | Empire [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 79.00% | |
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Cliffs Natural Resources [Member] | Tilden [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 85.00% | |
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Cliffs Natural Resources [Member] | Hibbing [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 23.00% | |
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Cliffs Natural Resources [Member] | Bloom Lake [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 75.00% | |
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Arcelor Mittal [Member] | Empire [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 21.00% | |
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Arcelor Mittal [Member] | Hibbing [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 62.30% | |
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U. S. Steel Canada | Tilden [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 15.00% | |
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U. S. Steel Canada | Hibbing [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 14.70% | |
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WISCO [Member] | Bloom Lake [Member]
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| Related Party Transaction [Line Items] | ||
| Ownership Interest | 25.00% |