Quarterly report pursuant to Section 13 or 15(d)

DERIVATIVE INSTRUMENTS (Narrative) (Details)

v3.10.0.1
DERIVATIVE INSTRUMENTS (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Jan. 01, 2018
Dec. 31, 2017
Derivative [Line Items]            
Natural Gas Hedges $ 3.4   $ 3.4     $ 3.5
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax (0.2)   (0.6)      
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net     0.1      
Derivative assets 174.7   174.7   $ 49.5 37.9
Derivative Liability 3.1   3.1     2.0
Not Designated as Hedging Instrument [Member]            
Derivative [Line Items]            
Derivative assets 174.6   174.6     37.9
Derivative Liability 3.0   3.0     1.7
Customer Supply Agreement [Member] | Not Designated as Hedging Instrument [Member] | Product Revenues [Member]            
Derivative [Line Items]            
Amount of gain/(loss) recognized in income on derivative (155.5) $ (51.9) (197.4) $ (69.6)    
Customer Supply Agreement [Member] | Not Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Assets [Member]            
Derivative [Line Items]            
Derivative assets 169.4   169.4     37.9
Provisional Pricing Arrangements [Member] | Not Designated as Hedging Instrument [Member] | Product Revenues [Member]            
Derivative [Line Items]            
Amount of gain/(loss) recognized in income on derivative 0.8 $ 21.1 (1.1) $ 5.3    
Provisional Pricing Arrangements [Member] | Not Designated as Hedging Instrument [Member] | Derivative Financial Instruments, Assets [Member]            
Derivative [Line Items]            
Derivative assets $ 5.2   $ 5.2     $ 0.0