DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Derivative Instruments in Statement of Financial Position) (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Net Total		$ (236.5)	$ (160.9)
Cash collateral held		11.5	28.4
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Net Total		126.8	185.5
Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Net Total		54.0	93.3
Accounts Payable and Other [Member]
Derivatives, Fair Value [Line Items]
Net Total	[1]	(305.1)	(315.4)
Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Net Total		$ (112.2)	(124.6)
Due from General Partner and Affiliates [Member]
Derivatives, Fair Value [Line Items]
Net Total			$ 0.3

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