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DEBT AND CREDIT FACILITIES (Debt Restructuring) (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Extinguishment of Debt [Line Items] |  |  |  |  |
Debt Instrument, Face Amount Exchanged |  |  |  | $ 512.2 |
Gain (loss) on extinguishment/restructuring of debt |  | $ 174.3 | $ (165.4) | 166.3 | $ 392.9
Debt, carrying value |  |  |  | 297.3 |
$544.2 Million 7.75% 2020 Second Lien Notes [Member] |  |  |  |  |
Extinguishment of Debt [Line Items] |  |  |  |  |
Debt Instrument, Face Amount Exchanged |  |  |  | 114.1 |
Debt Instrument, Face Amount Received in Debt Exchange of $544M 7.75% Notes |  |  |  | 57.0 |
Gain (loss) on extinguishment/restructuring of debt |  |  | (104.5) | 6.9 |
Debt Instrument, Par Value |  |  |  | 430.1 |
Debt, carrying value |  |  |  | 77.5 |
Five Hundred Million Three Point Nine Five Two Thousand Eighteen Senior Note [Member] |  |  |  |  |
Extinguishment of Debt [Line Items] |  |  |  |  |
Debt Instrument, Face Amount Exchanged |  |  |  | 17.6 |
Debt Instrument, Face Amount Received in Debt Exchange of $500M 3.95% Notes |  |  |  | 11.4 |
Gain (loss) on extinguishment/restructuring of debt | $ 19.9 |  |  | 1.8 |
Debt, carrying value |  |  |  | 15.5 |
Four Hundred Million Five Point Nine Zero Two Thousand And Twenty Senior Note [Member] |  |  |  |  |
Extinguishment of Debt [Line Items] |  |  |  |  |
Debt Instrument, Face Amount Exchanged |  |  |  | 65.1 |
Debt Instrument, Face Amount Received in Debt Exchange of $400M 5.90% Notes |  |  |  | 26.0 |
Gain (loss) on extinguishment/restructuring of debt |  |  | (7.8) | 28.3 |
Debt Instrument, Par Value | 88.9 |  | 88.9 | 225.6 |
Debt, carrying value |  |  |  | 35.4 |
$500 Million 4.80% 2020 Senior Notes[Member] |  |  |  |  |
Extinguishment of Debt [Line Items] |  |  |  |  |
Debt Instrument, Face Amount Exchanged |  |  |  | 44.7 |
Debt Instrument, Face Amount Received in Debt Exchange of $500M 4.80% Notes |  |  |  | 17.9 |
Gain (loss) on extinguishment/restructuring of debt | 0.6 |  | (1.9) | 19.5 |
Debt Instrument, Par Value | 122.4 |  | 122.4 | 236.8 |
Debt, carrying value |  |  |  | 24.4 |
$700 Million 4.875% 2021 Senior Notes[Member] |  |  |  |  |
Extinguishment of Debt [Line Items] |  |  |  |  |
Debt Instrument, Face Amount Exchanged |  |  |  | 76.3 |
Debt instrument, Face Amount Received in Debt Exchange of $700M 4.875% Notes |  |  |  | 30.5 |
Gain (loss) on extinguishment/restructuring of debt |  |  | (2.8) | 33.3 |
Debt Instrument, Par Value | 138.4 |  | 138.4 | 309.4 |
Debt, carrying value |  |  |  | 41.5 |
$800 Million 6.25% 2040 Senior Notes [Member] |  |  |  |  |
Extinguishment of Debt [Line Items] |  |  |  |  |
Debt Instrument, Face Amount Exchanged |  |  |  | 194.4 |
Debt Instrument, Face Amount Received in Debt Exchange of $800M 6.25% Notes |  |  |  | 75.7 |
Gain (loss) on extinguishment/restructuring of debt |  |  |  | 84.5 |
Debt Instrument, Par Value | $ 298.4 |  | 298.4 | 298.4 |
Debt, carrying value |  |  |  | 103.0 |
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member] |  |  |  |  |
Extinguishment of Debt [Line Items] |  |  |  |  |
Gain (loss) on extinguishment/restructuring of debt |  |  | $ 45.1 |  |
Debt Instrument, Par Value |  |  |  | $ 218.5 |

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