Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS (Narrative) (Details)

v3.19.3
FAIR VALUE MEASUREMENTS (Narrative) (Details) - USD ($)
$ in Millions
Sep. 30, 2019
Dec. 31, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative assets $ 72.8 $ 91.5
Derivative liability 32.6 3.7
Fair Value, Inputs, Level 1 [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative assets 0.0 0.0
Derivative liability 0.0 0.0
Fair Value, Inputs, Level 2 [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative assets 0.0 0.1
Derivative liability 2.4 3.7
Fair Value, Inputs, Level 3 [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative assets 72.8 91.4
Derivative liability 30.2 0.0
Not Designated as Hedging Instrument [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative assets 72.8 91.4
Derivative liability 30.2 0.0
Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Customer Supply Agreement [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative assets 71.2 89.3
Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative assets 1.6 $ 2.1
Derivative liability $ 30.2