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DEBT (Details 2) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Principal maturities of long-term debt    
2016 $ 100.0  
2017 100.0  
2018 100.0  
2019 1,439.0  
2020 433.0  
Thereafter 3,971.0  
Aggregate future principal maturities 6,143.0 $ 6,360.0
Other Fixed-Rate and Variable-Rate Debt Disclosures    
Estimated fair value of long-term debt 3,600.0 5,600.0
Debt carrying value 6,100.0 6,400.0
Letters of credit issued 70.0 $ 25.0
Revolving credit facility | Letter of Credit    
Other Fixed-Rate and Variable-Rate Debt Disclosures    
Letters of credit issued $ 49.0  
Pro Forma    
Other Variable-Rate Debt Disclosures    
Percentage of change in the variable interest rates 0.125%  
Effect of 1/8 percent change in interest rates $ 2.2