Derivative Instruments (Details 5) (Not Designated as Hedging Instrument, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Outstanding net asset (liability) [Roll Forward]
Outstanding net asset (liability), Beginning Balance	$ (398)	$ (301)
Additions/Change in value of existing contracts	(44)	(344)
Settled contracts	240	247
Outstanding net asset (liability), Ending Balance	(202)	(398)
NUGs
Outstanding net asset (liability) [Roll Forward]
Outstanding net asset (liability), Beginning Balance	(254)	(293)
Additions/Change in value of existing contracts	(23)	(201)
Settled contracts	75	240
Outstanding net asset (liability), Ending Balance	(202)	(254)
LCAPP
Outstanding net asset (liability) [Roll Forward]
Outstanding net asset (liability), Beginning Balance	(144)	0
Additions/Change in value of existing contracts	(22)	(144)
Settled contracts	166	0
Outstanding net asset (liability), Ending Balance	0	(144)
Regulated FTRs
Outstanding net asset (liability) [Roll Forward]
Outstanding net asset (liability), Beginning Balance	0	(8)
Additions/Change in value of existing contracts	1	1
Settled contracts	(1)	7
Outstanding net asset (liability), Ending Balance	$ 0	$ 0