XML 118 R25.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Commodity Derivative Gains (Losses)
 12 Months Ended
Dec. 31, 2019
Analysis of income and expense [abstract]  
Commodity Derivative Gains (Losses)
COMMODITY DERIVATIVE GAINS (LOSSES)
($ millions)
2019

 
2018

 
Realized gains (losses)
43.4

 
(259.8
)
 
Unrealized gains (losses)
(104.4
)
 
203.4

 
Commodity derivative losses
(61.0
)
 
(56.4
)