DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Derivative Balances by Counterparty Credit Quality) (Details) - USD ($) $ in Millions		Mar. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Net Total	[1]	$ (161.6)	$ (57.9)
AAA Rating [Member]
Derivative [Line Items]
Net Total		0.1	0.0
AA Rating [Member]
Derivative [Line Items]
Net Total	[1],[2]	(47.3)	(12.4)
A Rating [Member]
Derivative [Line Items]
Net Total	[1]	(44.1)	(10.5)
Lower than A [Member]
Derivative [Line Items]
Net Total	[1]	$ (70.3)	$ (35.0)

[1] As determined by nationally-recognized statistical ratings organizations.

[2] Includes $12.6 million of cash collateral at December 31, 2015.