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DISCONTINUED OPERATIONS (Narrative) (Details) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2015 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Discontinued Operation, Tax Effect of Discontinued Operation |  | $ (6,000,000) | $ (1,216,000,000) | $ (184,500,000)
Tangible Asset Impairment Charges |  |  | 537,800,000 |
Deconsolidation, Gain (Loss), Amount |  | (528,200,000) |  |
LOSS FROM DISCONTINUED OPERATIONS, net of tax |  | (892,100,000) | (8,368,000,000) | (517,100,000)
Potential Earn Out from North American Coal sale |  | 50,000,000 |  |
Canadian Entities [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Disposal Group, Including Discontinued Operation, Revenue |  | 11,300,000 | 563,500,000 | 978,700,000
Discontinued Operation, Tax Effect of Discontinued Operation |  | 5,800,000 | 913,700,000 | 188,700,000
Deconsolidation, Gain (Loss), Amount |  | (710,900,000) | 0 | 0
Disposal Group, including discontinued operations, Impairment of long-lived assets |  | 0 | (7,536,800,000) | (236,400,000)
Cost Method Investments |  | 0 |  |
Disposal Group, Including Discontinued Operation, Costs of Goods Sold |  | (11,100,000) | (808,400,000) | (1,082,000,000)
Eliminations with Continuing Operations |  | 0 | (53,600,000) | (217,300,000)
Disposal Group, Including Discontinued Operation, Gross Profit (Loss) |  | 200,000 | (298,500,000) | (320,600,000)
Disposal Group, Including Discontinued Operation, Operating Expense |  | (33,800,000) | (306,300,000) | (151,500,000)
Disposal Group, Including Discontinued Operation, Other Expense |  | (1,000,000) | (5,600,000) | (10,000,000)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax |  | (34,600,000) | (610,400,000) | (462,100,000)
LOSS FROM DISCONTINUED OPERATIONS, net of tax |  | (739,700,000) | (7,233,500,000) | (509,800,000)
North American Coal [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Disposal Group, Including Discontinued Operation, Revenue |  | 392,900,000 | 687,100,000 | 821,900,000
Discontinued Operations, Amounts Held in Escrow |  | 14,900,000 | 17,500,000 |
Discontinued Operation, Tax Effect of Discontinued Operation |  | 200,000 | 302,200,000 | (6,200,000)
Tangible Asset Impairment Charges | $ 73,400,000 |  |  |
Disposal Group, Including Discontinued Operation, Costs of Goods Sold |  | (449,200,000) | (822,900,000) | (836,400,000)
Disposal Group, Including Discontinued Operation, Gross Profit (Loss) |  | (56,300,000) | (135,800,000) | (14,500,000)
Disposal Group, Including Discontinued Operation, Operating Expense |  | (30,400,000) | (20,800,000) | (13,800,000)
Disposal Group, Including Discontinued Operation, Other Expense |  | (1,800,000) | (3,000,000) | (2,400,000)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax |  | (79,200,000) | (579,200,000) | (3,100,000)
LOSS FROM DISCONTINUED OPERATIONS, net of tax |  | (152,400,000) | (1,134,500,000) | $ (9,300,000)
Bloom Lake Group [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Deconsolidation, Gain (Loss), Amount |  | 818,700,000 |  |
Contingent Liabilities of Deconsolidated Entities |  | (203,100,000) |  |
Wabush Group [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Deconsolidation, Gain (Loss), Amount |  | 134,700,000 |  |
Asia Pacific Iron Ore [Member] | Asia Pacific Iron Ore [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Tangible Asset Impairment Charges |  |  | $ 526,500,000 |
Other Current Assets [Member] | Canadian Entities [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Pre-Petition Financing |  | 7,200,000 |  |
DIP Financing |  | 6,800,000 |  |
Guarantees [Member] | Bloom Lake Group [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Contingent Liabilities recognized in Consolidated Financials |  | 96,500,000 |  |
Other Current Liabilities [Member] | Bloom Lake Group [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Contingent Liabilities recognized in Consolidated Financials |  | 35,900,000 |  |
Fair Value, Inputs, Level 3 [Member] | Other Current Assets [Member] | Canadian Entities [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
Loans, Associated Interest and Accounts Receivable recognized in Consolidated Financials at Fair Value |  | 72,900,000 |  |
Maximum [Member] | Other Current Assets [Member] | Canadian Entities [Member] |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |
DIP Financing |  | $ 10,000,000 |  |

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