XML 65 R53.htm IDEA: XBRL DOCUMENT v3.7.0.1
Derivative Instruments (Details 4) - Not Designated as Hedging Instrument - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Outstanding net asset (liability) [Roll Forward]    
Outstanding net asset (liability), Beginning Balance $ (105) $ (135)
Unrealized loss (6) (13)
Settlements 6 11
Outstanding net asset (liability), Ending Balance (105) (137)
NUGs    
Outstanding net asset (liability) [Roll Forward]    
Outstanding net asset (liability), Beginning Balance (107) (136)
Unrealized loss (5) (12)
Settlements 9 13
Outstanding net asset (liability), Ending Balance (103) (135)
Regulated FTRs    
Outstanding net asset (liability) [Roll Forward]    
Outstanding net asset (liability), Beginning Balance 2 1
Unrealized loss (1) (1)
Settlements (3) (2)
Outstanding net asset (liability), Ending Balance $ (2) $ (2)