DERIVATIVE INSTRUMENTS (Schedule Of Derivatives Not Designated As Hedging Instruments) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 45.1	$ 32.2
Customer Supply Agreement [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/(loss) recognized in income on derivative	41.9	17.8
Provisional Pricing Arrangements [Member] | Product Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/(loss) recognized in income on derivative	3.2	15.7
Commodity Contract [Member] | Other Nonoperating Income (Expense) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 0.0	$ (1.3)