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INCOME TAXES (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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Income Tax Contingency [Line Items] |  |
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Pensions | $ 76.3 | $ 114.6
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits | 25.6 | 35.2
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax | 0.0 | 251.2
Deferred Tax Assets, Deferred Income | 24.2 | 44.5
Deferred Tax Assets, Goodwill and Intangible Assets | 12.2 | 0.0
Deferred Tax Assets, Amortization | 0.0 | 71.3
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Asset Retirement Obligations | 9.9 | 22.3
Deferred Tax Assets, Operating Loss Carryforwards | 2,368.1 | 2,699.7
Deferred Tax Assets, Property, Plant and Equipment | 188.2 | 181.2
Deferred Tax Assets, State Taxes | 74.2 | 59.2
Deferred Tax Assets Leasing Arrangements | 9.6 | 12.9
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Other | 100.4 | 108.3
Deferred Tax Assets, Gross | 2,888.7 | 3,600.4
Deferred Tax Assets, Valuation Allowance | (2,238.5) | (3,334.8)
Deferred Tax Assets, Net of Valuation Allowance | 650.2 | 265.6
Deferred Tax Liabilities, Property, Plant and Equipment | (1.5) | (34.0)
Deferred Tax Liabilities Investment In Ventures | (137.5) | (203.1)
Deferred Tax Liabilities, Intangible Assets | 0.0 | (1.0)
Deferred Tax Liabilities, Tax Deferred Income | (3.8) | (3.4)
Deferred Tax Liabilities, Intercompany Notes | 465.7 | 0.0
Deferred Tax Liabilities Other Assets | (41.7) | (24.1)
Deferred Tax Liabilities, Net | (650.2) | (265.6)
Deferred Tax Assets, Net | $ 0.0 | $ 0.0

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