Quarterly report pursuant to Section 13 or 15(d)

DERIVATIVE INSTRUMENTS (Schedule Of Derivatives Not Designated As Hedging Instruments) (Details)

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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)