Annual report pursuant to Section 13 and 15(d)

FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details)

v3.19.3.a.u2
FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
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
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
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
Valuation, Market Approach [Member] | Not Designated as Hedging Instrument [Member] | Derivative Asset [Member] | Customer Supply Agreements [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 44.5 89.3
Valuation, Market Approach [Member] | Not Designated as Hedging Instrument [Member] | Derivative Asset [Member] | Provisional Pricing Arrangements [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Asset 1.3 2.1
Valuation, Market Approach [Member] | Not Designated as Hedging Instrument [Member] | Other Current Liabilities [Member] | Provisional Pricing Arrangements [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Liability $ 1.1 $ 0.0