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 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]        
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ 154.7 $ 30.8 $ 198.5 $ 63.0
Customer Supply Agreement [Member] | Product Revenues [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Amount of gain/(loss) recognized in income on derivative 155.5 51.9 197.4 69.6
Provisional Pricing Arrangements [Member] | Product Revenues [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Amount of gain/(loss) recognized in income on derivative (0.8) (21.1) 1.1 (5.3)
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 $ 0.0 $ 0.0 $ (1.3)