Commodity And Other Derivative Contractual Assets And Liabilities (Concentrations of Credit Risk Related to Derivatives) (Details) (Texas Competitive Electric Holdings Company LLC [Member], Credit Risk Contract [Member], USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Texas Competitive Electric Holdings Company LLC [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Total credit risk exposure to all counterparties related to derivative contracts	$ 1,258
Net exposure to those counterparties after taking into effect master netting arrangements, setoff provisions and collateral	275
Credit risk exposure to banking and financial sector percentage	88.00%
Net exposure to banking and financial sector percentage	59.00%
Largest net Exposure to single counterparty	$ 50