DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Effect of Derivative Instruments on Consolidated Statements of Income) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Commodity Costs [Member] | Commodity Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain on Settlement of Derivative Instruments		$ 0.4	$ 1.2	$ 0.4	$ 3.7
Derivatives Not Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings	[1],[2]	1.4	(3.9)	3.1	(3.1)
Derivatives Not Designated As Hedging Instruments [Member] | Transportation And Other Services Revenue [Member] | Commodity Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Earnings	[1],[2],[3]	$ 1.4	$ (3.9)	$ 3.1	$ (3.1)

[1] Does not include settlements associated with derivative instruments that settle through physical delivery.

[2] Includes only net gains or losses associated with those derivatives that do not receive hedge accounting treatment and does not include the ineffective portion of derivatives that are designated as hedging instruments.

[3] Includes settlement gains of $0.4 million and $1.2 million for the three months ended June 30, 2017 and 2016, respectively and settlement gains of $0.4 million and $3.7 million for the six months ended June 30, 2017 and 2016, respectively.