DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details) - USD ($) $ in Millions			12 Months Ended
		Oct. 06, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative instruments income statement location of gain loss reclassified from accumulated other comprehensive income			$ 223.8	$ 255.5
Unrealized gain (Loss)				1.5
Cash flow hedge gain (loss) to be reclassified within twelve months			39.9
Expected value of cash collateral or letters of credit if credit rating is downgraded			60.1
Letters of credit provided on derivatives			119.5	120.1
Debt instrument amount			7,927.6	8,076.1
Debt Instrument, Unamortized Discount			6.2	6.2
Interest expense			445.5	322.0	$ 403.2
Cash Collateral for Borrowed Securities	[1]			12.6
Credit Concentration Risk [Member]
Derivative [Line Items]
Cash Collateral for Borrowed Securities				12.6
Other Assets [Member]
Derivative [Line Items]
Cash Collateral for Borrowed Securities				12.6
Senior Notes [Member]
Derivative [Line Items]
Debt instrument amount		$ 1,600.0	$ 200.0
Remaining amount of the effective portion of the hedge				232.1
Net proceeds after deducting underwriting discounts and commissions		1,575.0
Repayments of debt		$ 314.7
Debt Instrument, Unamortized Discount				6.2
Interest expense				82.6
Senior Notes [Member] | Maximum [Member]
Derivative [Line Items]
Amortized as interest expense over a term		10 years
Senior Notes [Member] | Minimum [Member]
Derivative [Line Items]
Amortized as interest expense over a term		8 years
Counterparty Credit Quality [Member]
Derivative [Line Items]
Cash Collateral for Borrowed Securities				12.6
Amended Interest Rate Hedges [Member]
Derivative [Line Items]
Unrealized gains (losses) on interest rate hedge ineffectiveness				$ 96.2	$ 100.6

[1] Includes settlement gains of $5.5 million, $26.9 million, and $4.5 million for the years ended December 31, 2016, 2015 and 2014, respectively.