Annual report pursuant to Section 13 and 15(d)

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details)

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DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Derivatives, Fair Value [Line Items]    
Derivative Asset $ 45.8 $ 91.5
Derivative Liability 4.3 3.7
Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 45.8 91.4
Derivative Liability 1.1 0.0
Fair Value, Inputs, Level 2 [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 0.0 0.1
Derivative Liability 3.2 3.7
Fair Value, Inputs, Level 3 [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 45.8 91.4
Derivative Liability 1.1 0.0
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Derivative Asset [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 0.0 0.1
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability 3.2 3.7
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Customer Supply Agreements [Member] | Derivative Asset [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 44.5 89.3
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Derivative Asset [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset 1.3 2.1
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability $ 1.1 $ 0.0