Derivative Instruments (Details 3) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Sale of Derivatives	$ 86	[1]	$ 230	[1]	$ (50)	[1]
Unrealized Gain (Loss) on Derivatives	(12)	[2]	72	[2]	30	[2]
Gain (Loss) on Derivative Instruments, Net, Pretax	74		302		(20)
Power contracts included in operating revenues	(119)		187		(20)
Natural gas contracts included in fuel and purchased energy expense	191		118		138
Interest rate swaps included in interest expense	2		11		7
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	0		(14)		(145)
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Sale of Derivatives	0	[1]	(157)	[1]	(193)	[1]
Unrealized Gain (Loss) on Derivatives	2	[2]	154	[2]	55	[2]
Commodity Option [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Sale of Derivatives	86	[1]	387	[1]	143	[1]
Unrealized Gain (Loss) on Derivatives	$ (14)	[2]	$ (82)	[2]	$ (25)	[2]

[1] Does not include the realized value associated with derivative instruments that settle through physical delivery.

[2] In addition to changes in market value on derivatives not designated as hedges, changes in unrealized gain (loss) also includes hedge ineffectiveness and adjustments to reflect changes in credit default risk exposure.