Annual report pursuant to Section 13 and 15(d)

DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Debt Restructuring) (Details)

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DEBT AND CREDIT FACILITIES DEBT AND CREDIT FACILITIES (Debt Restructuring) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Mar. 31, 2016
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Extinguishment of Debt [Line Items]              
Debt Instrument, Face Amount Exchanged     $ 512.2 $ 674.6      
Gain on extinguishment/restructuring of debt         $ 166.3 $ 392.9 $ 16.2
$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 $400M 5.90% Notes       57.5      
Debt Instrument, Face Amount Received in Debt Exchange of $500M 4.80% Notes       112.9      
Debt instrument, Face Amount Received in Debt Exchange of $700M 4.875% Notes       170.3      
Debt Instrument, Face Amount Received in Debt Exchange of $800M 6.25% Notes       203.5      
Debt Instrument, Carrying Amount Received in Debt Exchange of $400M 5.90% Notes       42.0      
Debt Instrument, Carrying Value Received in Debt Exchange of $500M 4.80% Notes       82.4      
Debt instrument, Carrying Value Received in Debt Exchange of $700M 4.875% Notes       124.3      
Debt Instrument, Carrying Value Received in Debt Exchange of $800M 6.25% Notes       148.5      
Debt Instrument, Par Value $ 430.1     544.2 430.1 544.2  
Debt, carrying value       397.2      
$544.2 Million 7.75% 2020 Second Lien Notes [Member] | Exchange of Debt [Member]              
Extinguishment of Debt [Line Items]              
Gain on extinguishment/restructuring of debt     6.9     269.5  
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        
Gain on extinguishment/restructuring of debt   $ (19.9)          
Debt Instrument, Par Value           311.2  
Five Hundred Million Three Point Nine Five Two Thousand Eighteen Senior Note [Member] | Exchange of Debt [Member]              
Extinguishment of Debt [Line Items]              
Gain on extinguishment/restructuring of debt     1.8        
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 67.0      
Debt Instrument, Par Value 225.6       225.6 290.8  
Four Hundred Million Five Point Nine Zero Two Thousand And Twenty Senior Note [Member] | Exchange of Debt [Member]              
Extinguishment of Debt [Line Items]              
Gain on extinguishment/restructuring of debt     28.3 24.5      
$500 Million 4.80% 2020 Senior Notes[Member]              
Extinguishment of Debt [Line Items]              
Debt Instrument, Face Amount Exchanged     44.7 137.8      
Gain on extinguishment/restructuring of debt 0.6            
Debt Instrument, Par Value 236.8       236.8 306.7  
$500 Million 4.80% 2020 Senior Notes[Member] | Exchange of Debt [Member]              
Extinguishment of Debt [Line Items]              
Gain on extinguishment/restructuring of debt     19.5 54.6      
$700 Million 4.875% 2021 Senior Notes[Member]              
Extinguishment of Debt [Line Items]              
Debt Instrument, Face Amount Exchanged     76.3 208.5      
Debt Instrument, Par Value 309.4       309.4 412.5  
$700 Million 4.875% 2021 Senior Notes[Member] | Exchange of Debt [Member]              
Extinguishment of Debt [Line Items]              
Gain on extinguishment/restructuring of debt     33.3 83.1      
$800 Million 6.25% 2040 Senior Notes [Member]              
Extinguishment of Debt [Line Items]              
Debt Instrument, Face Amount Exchanged     194.4 261.3      
Debt Instrument, Par Value 298.4       298.4 $ 492.8  
$800 Million 6.25% 2040 Senior Notes [Member] | Exchange of Debt [Member]              
Extinguishment of Debt [Line Items]              
Gain on extinguishment/restructuring of debt     84.5 $ 107.3      
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member]              
Extinguishment of Debt [Line Items]              
Debt Instrument, Face Amount Received in Debt Exchange of $544M 7.75% Notes     57.0        
Debt Instrument, Face Amount Received in Debt Exchange of $500M 3.95% Notes     11.4        
Debt Instrument, Face Amount Received in Debt Exchange of $400M 5.90% Notes     26.0        
Debt Instrument, Face Amount Received in Debt Exchange of $500M 4.80% Notes     17.9        
Debt instrument, Face Amount Received in Debt Exchange of $700M 4.875% Notes     30.5        
Debt Instrument, Face Amount Received in Debt Exchange of $800M 6.25% Notes     75.7        
Debt Instrument, Carrying Amount Received in Debt Exchange of $544.2M 7.75% Notes     77.5        
Debt Instrument, Carrying Amount Received in Debt Exchange of $500M 3.95% Notes     15.5        
Debt Instrument, Carrying Amount Received in Debt Exchange of $400M 5.90% Notes     35.4        
Debt Instrument, Carrying Value Received in Debt Exchange of $500M 4.80% Notes     24.4        
Debt instrument, Carrying Value Received in Debt Exchange of $700M 4.875% Notes     41.5        
Debt Instrument, Carrying Value Received in Debt Exchange of $800M 6.25% Notes     103.0        
Debt Instrument, Par Value $ 218.5   218.5   218.5    
Debt, carrying value     $ 297.3        
$218.5 Million 8.00% 2020 1.5 Lien Notes [Member] | Exchange of Debt [Member]              
Extinguishment of Debt [Line Items]              
Gain on extinguishment/restructuring of debt         $ 174.3