Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS (Narrative) (Details)

v3.19.2
FAIR VALUE MEASUREMENTS (Narrative) (Details) - USD ($)
$ in Millions
Jun. 30, 2019
Dec. 31, 2018
Fair Value Assets And Liabilities Components [Line Items]    
Derivative assets $ 118.3 $ 91.5
Derivative liability 2.6 3.7
Fair Value, Inputs, Level 1 [Member]    
Fair Value Assets And Liabilities Components [Line Items]    
Derivative assets 0.0 0.0
Derivative liability 0.0 0.0
Fair Value, Inputs, Level 2 [Member]    
Fair Value Assets And Liabilities Components [Line Items]    
Derivative assets 0.2 0.1
Derivative liability 2.6 3.7
Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Components [Line Items]    
Derivative assets 118.1 91.4
Derivative liability   0.0
Not Designated as Hedging Instrument [Member]    
Fair Value Assets And Liabilities Components [Line Items]    
Derivative assets 118.1 91.4
Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Customer Supply Agreement [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Components [Line Items]    
Derivative assets 102.4 89.3
Other Current Assets [Member] | Not Designated as Hedging Instrument [Member] | Valuation, Market Approach [Member] | Provisional Pricing Arrangements [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Components [Line Items]    
Derivative assets 15.7 $ 2.1
Derivative liability $ 0.0