Annual report pursuant to Section 13 and 15(d)

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

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FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule Of Quantitative Inputs And Assumptions For Level 3 Assets And Liabilities) (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset $ 45.8 $ 91.5
Derivative Liability 4.3 3.7
Not Designated as Hedging Instrument [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 45.8 91.4
Derivative Liability 1.1 0.0
Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 45.8 91.4
Derivative Liability 1.1 0.0
Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Liability 1.1 0.0
Derivative Asset [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 1.3 2.1
Derivative Asset [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Customer Supply Agreements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset $ 44.5 $ 89.3
Managements Estimate Of 62% Fe [Member] | Weighted Average [Member] | Derivative Asset [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 76  
Customer's Hot-Rolled Steel Estimate [Member] | Weighted Average [Member] | Derivative Asset [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Customer Supply Agreements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 650  
PPI Estimates [Member] | Weighted Average [Member] | Other Current Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value, Measurement With Unobservable Inputs Range 197