DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Derivative Balances by Counterparty Credit Quality) (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Net Total		$ (236.5)	$ (160.9)
Cash collateral held		11.5	28.4
AAA Rating [Member]
Derivative [Line Items]
Net Total	[1]	0.1	0.1
AA Rating [Member]
Derivative [Line Items]
Net Total	[1],[2]	(68.5)	(49.8)
Cash collateral held		11.5	28.4
A Rating [Member]
Derivative [Line Items]
Net Total	[1]	(84.5)	(129.1)
Lower than A [Member]
Derivative [Line Items]
Net Total	[1]	$ (83.6)	$ 17.9

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

[2] Includes $11.5 million and $28.4 million held of cash collateral at June 30, 2015 and December 31, 2014, respectively.