Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS (Narrative) (Details)

v3.20.1
FAIR VALUE MEASUREMENTS (Narrative) (Details) - Not Designated as Hedging Instrument [Member] - Valuation, Market Approach [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($)
$ in Millions
Mar. 31, 2020
Dec. 31, 2019
Customer Supply Agreement [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative Asset $ 19.0 $ 44.5
Provisional Pricing Arrangements [Member]    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivative Asset 0.6 1.3
Derivative liability $ 0.0 $ (1.1)