Price Risk Management Assets And Liabilities Fair Value of Derivatives, Netting Basis (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ (83)	$ 65	$ (71)	$ 45
Derivative Asset, Fair Value, Gross Asset	110		110		316
Derivative Liability, Fair Value, Gross Liability	(242)		(242)		(360)
Derivative Asset, Fair Value, Amount Offset Against Collateral	(46)		(46)		(37)
Derivative Liability, Fair Value, Amount Offset Against Collateral	73		73		91
Netting [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	153		153		306
Derivative Liability, Fair Value, Gross Liability	194		194		356
Derivative Asset, Fair Value, Gross Liability	(38)		(38)		(36)
Derivative Liability, Fair Value, Gross Asset	38		38		36
Derivative Asset, Fair Value, Net	107		107		269
Derivative Liability, Fair Value, Net	(121)		(121)		(265)
Bi-lateral contracts [Member] | Netting [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	47		47		41
Derivative Liability, Fair Value, Gross Liability	44		44		38
Broker cleared derivative contracts [Member] | Netting [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	106		106		265
Derivative Liability, Fair Value, Gross Liability	150		150		318
Asset Fair Value, Netting Offset [Member] | Netting [Member]
Derivative [Line Items]
Payments on Margin Deposits	(8)		(8)		(1)
Other Derivatives Not Designated as Hedging Instruments Assets at Fair Value	3		3		47
Liability Fair Value, Netting Offset [Member] | Netting [Member]
Derivative [Line Items]
Payments on Margin Deposits	35		35		55
Other Derivatives Not Designated as Hedging Instruments Liabilities at Fair Value	$ (121)		$ (121)		$ (95)