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DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivatives Not Designated As Hedging Instruments) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net | $ 7.5 | $ 422.6 | $ 119.3
Product Revenues [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net |  |  | 120.6
Customer Supply Agreements [Member] | Product Revenues [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net | 78.1 | 425.8 | 163.3
Provisional Pricing Arrangements [Member] | Product Revenues [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net | (70.6) | (3.2) | (42.7)
Commodity Contract [Member] | Cost of goods sold and operating expenses [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net | $ 0.0 | $ 0.0 | $ (1.3)

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