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QUARTERLY RESULTS OF OPERATIONS (Details) - USD ($) shares in Millions, $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | 25.2 | 25.3 | 25.2 | 0.0
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements | 0.5 |  | 0.7 |
Gain Contingency on North American Coal Sale |  | $ 50.0 |  |
Loss (gain) on sale of North American Coal mines | $ 419.6 |  | $ 155.0 |
Sale Price of CLCC Assets | 174.0 |  | 174.0 |
Proceeds from sale of Cliffs Logan County Coal | 155.0 |  |  |
Income Tax Expense (Benefit) | (207.3) | 169.3 | (86.0) | $ 237.6
Asset Impairment Charges |  | $ 3.3 | $ 635.5 | $ 14.3
Minimum [Member] |  |  |  |
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount |  | 25.2 |  |
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements |  | 0.1 |  |
Maximum [Member] |  |  |  |
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount |  | 25.6 |  |
Antidilutive Incremental Common Shares Excluded and Attributable to Share-based Payment Arrangements |  | 0.3 |  |
Continuing Operations [Member] |  |  |  |
Asset Impairment Charges | 256.9 |  |  |
Discontinued Operations [Member] |  |  |  |
Asset Impairment Charges | $ 1,000.0 |  |  |

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