Price Risk Management Assets And Liabilities Table - Gross FV and Netting Offset (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 193	$ 320
Derivative Liability, Fair Value, Gross Liability	(331)	(389)
Derivative Asset, Fair Value, Amount Offset Against Collateral	(62)	(37)
Derivative Liability, Fair Value, Amount Offset Against Collateral	106	91
Netting [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	248	306
Derivative Liability, Fair Value, Gross Liability	(310)	(356)
Derivative Asset, Fair Value, Gross Liability	(52)	(36)
Derivative Liability, Fair Value, Gross Asset	52	36
Derivative Asset, Fair Value, Net	186	269
Derivative Liability, Fair Value, Net	(204)	(265)
Netting [Member] | Bi-lateral contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	60	42
Derivative Liability, Fair Value, Gross Liability	(56)	(38)
Netting [Member] | Broker cleared derivative contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	188	264
Derivative Liability, Fair Value, Gross Liability	(254)	(318)
Netting [Member] | Asset Fair Value, Netting Offset [Member]
Derivatives, Fair Value [Line Items]
Payments on Margin Deposits	(10)	(1)
Other Derivatives Not Designated as Hedging Instruments Assets at Fair Value	7	51
Netting [Member] | Liability Fair Value, Netting Offset [Member]
Derivatives, Fair Value [Line Items]
Payments on Margin Deposits	54	55
Other Derivatives Not Designated as Hedging Instruments Liabilities at Fair Value	$ (127)	$ (124)