XML 104 R80.htm IDEA: XBRL DOCUMENT v3.10.0.1
Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Jun. 30, 2017
State [Line Items]      
Revenue Capitalized During Pre-Commercial Operations $ 0 $ 1 $ 1
Electric revenue (2,681) (2,509)  
Other revenue 44 40  
ALABAMA      
State [Line Items]      
Electric revenue (392) (361)  
GEORGIA      
State [Line Items]      
Electric revenue (67) (63)  
KENTUCKY      
State [Line Items]      
Electric revenue (168) (159)  
MISSISSIPPI      
State [Line Items]      
Electric revenue (251) (237)  
NORTH CAROLINA      
State [Line Items]      
Electric revenue (20) (16)  
TENNESSEE      
State [Line Items]      
Electric revenue (1,771) (1,660)  
VIRGINIA      
State [Line Items]      
Electric revenue $ (12) $ (12)