DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Reconciliation of Changes in Fair Value of L3 Assets and Liabilities on Recurring Basis) (Details) $ in Millions		6 Months Ended
		Jun. 30, 2015 USD ($)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance		$ 168.9
Transfer in (out) of Level 3	[1]
Reported in Other comprehensive income (loss), net of tax		$ (0.4)
Purchases, issuances, sales and settlements:
Purchases
Sales		$ 2.0
Settlements	[2]	(73.0)
Ending balance		108.4
Commodity Sales [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains or losses included in earnings		3.8
Purchases, issuances, sales and settlements:
Amounts reported in Commodity sales		(15.5)
Amount of changes in net assets attributable to the change in derivative gains or losses related to assets and liabilities still held at the reporting date		5.6
Commodity Costs [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains or losses included in earnings		7.1
Purchases, issuances, sales and settlements:
Amount of changes in net assets attributable to the change in derivative gains or losses related to assets and liabilities still held at the reporting date		2.9
Commodity Contracts - Financial [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance		$ 42.7
Transfer in (out) of Level 3	[1]
Reported in Other comprehensive income (loss), net of tax		$ (0.4)
Purchases, issuances, sales and settlements:
Purchases
Sales
Settlements	[2]	$ (20.0)
Ending balance		$ 20.1
Commodity Contracts - Financial [Member] | Commodity Sales [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains or losses included in earnings
Purchases, issuances, sales and settlements:
Amounts reported in Commodity sales
Amount of changes in net assets attributable to the change in derivative gains or losses related to assets and liabilities still held at the reporting date
Commodity Contracts - Financial [Member] | Commodity Costs [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains or losses included in earnings		$ (2.2)
Purchases, issuances, sales and settlements:
Amount of changes in net assets attributable to the change in derivative gains or losses related to assets and liabilities still held at the reporting date		(2.0)
Commodity Contracts - Physical [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance		$ 19.5
Transfer in (out) of Level 3	[1]
Reported in Other comprehensive income (loss), net of tax
Purchases, issuances, sales and settlements:
Purchases
Sales
Settlements	[2]	$ (24.2)
Ending balance		12.3
Commodity Contracts - Physical [Member] | Commodity Sales [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains or losses included in earnings		3.8
Purchases, issuances, sales and settlements:
Amounts reported in Commodity sales		(15.5)
Amount of changes in net assets attributable to the change in derivative gains or losses related to assets and liabilities still held at the reporting date		5.6
Commodity Contracts - Physical [Member] | Commodity Costs [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains or losses included in earnings		13.2
Purchases, issuances, sales and settlements:
Amount of changes in net assets attributable to the change in derivative gains or losses related to assets and liabilities still held at the reporting date		5.8
Commodity Options [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance		$ 106.7
Transfer in (out) of Level 3	[1]
Reported in Other comprehensive income (loss), net of tax
Purchases, issuances, sales and settlements:
Purchases
Sales		$ 2.0
Settlements	[2]	(28.8)
Ending balance		$ 76.0
Commodity Options [Member] | Commodity Sales [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains or losses included in earnings
Purchases, issuances, sales and settlements:
Amounts reported in Commodity sales
Amount of changes in net assets attributable to the change in derivative gains or losses related to assets and liabilities still held at the reporting date
Commodity Options [Member] | Commodity Costs [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains or losses included in earnings		$ (3.9)
Purchases, issuances, sales and settlements:
Amount of changes in net assets attributable to the change in derivative gains or losses related to assets and liabilities still held at the reporting date		$ (0.9)

[1] Our policy is to recognize transfers as of the last day of the reporting period.

[2] Settlements represent the realized portion of forward contracts.