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		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Derivative [Line Items]
Unrealized Gain (Loss) to Derivative Instrument	$ (199)	$ (145)	$ (279)	$ (234)
Realized Gain (Loss) to Derivative Instrument	66	62	142	124
NUGs
Derivative [Line Items]
Unrealized Gain (Loss) to Derivative Instrument	(54)	(147)	(133)	(236)
Realized Gain (Loss) to Derivative Instrument	61	62	133	134
LCAPP
Derivative [Line Items]
Unrealized Gain (Loss) to Derivative Instrument	(145)	0	(145)	0
Realized Gain (Loss) to Derivative Instrument	0	0	0	0
Regulated FTRs
Derivative [Line Items]
Unrealized Gain (Loss) to Derivative Instrument	0	2	(1)	2
Realized Gain (Loss) to Derivative Instrument	5	0	9	(10)
Other
Derivative [Line Items]
Unrealized Gain (Loss) to Derivative Instrument	0	0	0	0
Realized Gain (Loss) to Derivative Instrument	$ 0	$ 0	$ 0	$ 0