DERIVATIVE INSTRUMENTS (Schedule Of Derivative Instruments In Statement Of Financial Position, Fair Value) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Commodity Contract [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 1.6
Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	26.5	$ 3.2
Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	3.4
Foreign Exchange Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	1.6
Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	0.9
Customer Supply Agreement [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	19.0	44.5
Provisional Pricing Arrangements [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0.6	1.3
Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability		1.1
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	1.6
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	26.5	3.2
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	3.4
Fair Value, Inputs, Level 2 [Member] | Foreign Exchange Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	1.6
Fair Value, Inputs, Level 2 [Member] | Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	0.9
Fair Value, Inputs, Level 2 [Member] | Customer Supply Agreement [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0.0
Fair Value, Inputs, Level 2 [Member] | Provisional Pricing Arrangements [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0.0
Fair Value, Inputs, Level 2 [Member] | Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability		0.0
Fair Value, Inputs, Level 3 [Member] | Commodity Contract [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0.0
Fair Value, Inputs, Level 3 [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Customer Supply Agreement [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	19.0	44.5
Fair Value, Inputs, Level 3 [Member] | Provisional Pricing Arrangements [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0.6	1.3
Fair Value, Inputs, Level 3 [Member] | Provisional Pricing Arrangements [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability		1.1
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	0.3	0.0
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	(25.9)	(3.2)
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	(2.8)	0.0
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	(1.6)	0.0
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	(0.9)	0.0
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	1.3	0.0
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	(0.6)	0.0
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	(0.6)	0.0
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Customer Supply Agreement [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	19.0	44.5
Valuation, Market Approach [Member] | Fair Value, Inputs, Level 3 [Member] | Not Designated as Hedging Instrument [Member] | Provisional Pricing Arrangements [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0.6	1.3
Derivative liability	$ 0.0	$ (1.1)