Derivative Instruments (Details 4) (Not Designated as Hedging Instrument, Subject to Regulatory Accounting, Excluded from Earnings, USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	$ (50)	$ (199)	$ (34)	$ (279)
Realized Gain (Loss) on Derivative Instrument	21	66	43	142
NUGs
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	(38)	(54)	(20)	(133)
Realized Gain (Loss) on Derivative Instrument	20	61	43	133
LCAPP
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	(12)	(145)	(14)	(145)
Realized Gain (Loss) on Derivative Instrument	0	0	0	0
Regulated FTRs
Derivative [Line Items]
Unrealized Gain (Loss) on Derivative Instrument	0	0	0	(1)
Realized Gain (Loss) on Derivative Instrument	$ 1	$ 5	$ 0	$ 9