Derivative Instruments (Details 3) (Not Designated as Hedging Instrument [Member], Subject to Regulatory Accounting, Excluded from Earnings, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	$ (47)	$ (92)	$ (325)	$ (325)
Realized Gain (Loss) on Derivative Instrument	60	50	201	173
NUGs
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	(50)	(89)	(183)	(325)
Realized Gain (Loss) on Derivative Instrument	61	53	194	187
LCAPP
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	3	0	(142)	0
Realized Gain (Loss) on Derivative Instrument	0	0	0	0
Regulated FTRs
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	0	(3)	0	0
Realized Gain (Loss) on Derivative Instrument	(1)	(3)	7	(4)
Other
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	0	0	0	0
Realized Gain (Loss) on Derivative Instrument	$ 0	$ 0	$ 0	$ (10)