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COMMITMENTS AND CONTINGENCIES Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Loss Contingencies [Line Items] |  |  |  |  |
Loans to and accounts receivable from the Canadian Entities | $ 51.9 |  | $ 51.9 |  | $ 48.6
Contingent claims | 50.0 |  | 50.0 |  | 0.0
Contingent Liabilities recognized in Consolidated Financials | 0.0 |  | 0.0 |  | 37.2
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAX | 32.3 | $ (2.7) | (13.6) | $ (0.6) |
Wabush Scully Mine Sale [Member] |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, NET OF TAX | 31.4 |  |  |  |
Michigan Electricity Matters [Member] |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Loss Contingency Accrual | 13.6 |  | 13.6 |  |
Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |
Loans to and accounts receivable from the Canadian Entities |  |  |  |  | $ 48.6
Contingent Liabilities recognized in Consolidated Financials | $ 0.0 |  | $ 0.0 |  |

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