DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Derivative [Line Items]
Derivative instruments income statement location of gain loss reclassified from accumulated other comprehensive income	$ 247.6		$ 255.5
Unrealized gain (Loss)		$ 0.6
Cash flow hedge gain (loss) to be reclassified within twelve months	50.0
Expected value of cash collateral or letters of credit if credit rating is downgraded	62.9
Letters of credit provided on derivatives	$ 198.2		120.1
Cash Collateral for Borrowed Securities			12.6
Other Assets [Member]
Derivative [Line Items]
Cash Collateral for Borrowed Securities			12.6
Counterparty Credit Quality [Member]
Derivative [Line Items]
Cash Collateral for Borrowed Securities			$ 12.6