Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details)

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FAIR VALUE MEASUREMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details) - Fair Value, Inputs, Level 3 [Member] - Not Designated as Hedging Instrument [Member] - Valuation, Market Approach [Member]
$ in Millions
 3 Months Ended
Mar. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Customer Supply Agreement [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset $ 19.0 $ 44.5
Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset $ 0.6 $ 1.3
PPI Estimates [Member] | Provisional Pricing Arrangements [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 136.5  
Customer's Hot-Rolled Steel Estimate [Member] | Customer Supply Agreement [Member] | Weighted Average [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 559