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FAIR VALUE OF FINANCIAL INSTRUMENTS FAIR VALUE OF FINANCIAL INSTRUMENTS (Impairment Charges on Financial and Nonfinancial Assets) (Details) (USD $)
In Millions, unless otherwise specified
|
3 Months Ended |
12 Months Ended |
|
Mar. 31, 2014
|
Dec. 31, 2013
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Goodwill, Impairment Loss |
$ 0
|
$ 80.9
|
| ASSETS: |
|
|
| Assets, Fair Value Disclosure, Nonrecurring |
|
47.9
|
| Impairment Charges |
|
318.4
|
|
Fair Value, Inputs, Level 1 [Member]
|
|
|
| ASSETS: |
|
|
| Assets, Fair Value Disclosure, Nonrecurring |
|
0
|
|
Fair Value, Inputs, Level 2 [Member]
|
|
|
| ASSETS: |
|
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| Assets, Fair Value Disclosure, Nonrecurring |
|
0
|
|
Fair Value, Inputs, Level 3 [Member]
|
|
|
| ASSETS: |
|
|
| Assets, Fair Value Disclosure, Nonrecurring |
|
47.9
|
|
Amapa [Member]
|
|
|
| ASSETS: |
|
|
| Equity Method Investments, Fair Value Disclosure |
|
0
|
| Equity Method Investment, Other than Temporary Impairment |
|
67.6
|
|
Amapa [Member] | Fair Value, Inputs, Level 1 [Member]
|
|
|
| ASSETS: |
|
|
| Equity Method Investments, Fair Value Disclosure |
|
0
|
|
Amapa [Member] | Fair Value, Inputs, Level 2 [Member]
|
|
|
| ASSETS: |
|
|
| Equity Method Investments, Fair Value Disclosure |
|
0
|
|
Amapa [Member] | Fair Value, Inputs, Level 3 [Member]
|
|
|
| ASSETS: |
|
|
| Equity Method Investments, Fair Value Disclosure |
|
0
|
|
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Goodwill, Fair Value Disclosure |
|
0
|
| Goodwill, Impairment Loss |
|
80.9
|
|
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 1 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Goodwill, Fair Value Disclosure |
|
0
|
|
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 2 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Goodwill, Fair Value Disclosure |
|
0
|
|
Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 3 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Goodwill, Fair Value Disclosure |
|
0
|
|
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Property, Plant, and Equipment, Fair Value Disclosure |
|
46.3
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| Impairment of Long-Lived Assets Held-for-use |
|
155.4
|
|
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 1 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Property, Plant, and Equipment, Fair Value Disclosure |
|
0
|
|
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 2 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Property, Plant, and Equipment, Fair Value Disclosure |
|
0
|
|
Wabush and Cliffs Chromite Ontario and Cliffs Chromite Far North [Member] | Fair Value, Inputs, Level 3 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Property, Plant, and Equipment, Fair Value Disclosure |
|
46.3
|
|
Wabush [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Finite-lived Intangible Assets, Fair Value Disclosure |
|
1.6
|
| Other Asset Impairment Charges |
|
14.5
|
|
Wabush [Member] | Fair Value, Inputs, Level 1 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Finite-lived Intangible Assets, Fair Value Disclosure |
|
0
|
|
Wabush [Member] | Fair Value, Inputs, Level 2 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Finite-lived Intangible Assets, Fair Value Disclosure |
|
0
|
|
Wabush [Member] | Fair Value, Inputs, Level 3 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
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| Finite-lived Intangible Assets, Fair Value Disclosure |
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$ 1.6
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