DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Derivative Balances by Counterparty Credit Quality) (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Net Total	[1]	$ (181.6)	$ (166.7)
AA Rating [Member]
Derivative [Line Items]
Net Total	[1]	(82.6)	(79.2)
A Rating [Member]
Derivative [Line Items]
Net Total	[1]	(63.6)	(58.4)
Lower than A [Member]
Derivative [Line Items]
Net Total	[1]	$ (35.4)	$ (29.1)

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