Annual report pursuant to Section 13 and 15(d)

DEBT AND CREDIT FACILITIES (Debt Restructuring) (Details)

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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