Regulatory Assets, Liabilities, And Balancing Accounts (Long-Term Regulatory Assets) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Regulatory Assets [Line Items]
Regulatory assets	$ 5,714	$ 5,846
Pension Benefits [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,801	1,759
Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory assets	1,371	1,250
Utility Retained Generation [Member]
Regulatory Assets [Line Items]
Regulatory assets	628	666
Energy Recovery Bonds [Member]
Regulatory Assets [Line Items]
Regulatory assets	435	735
Environmental Compliance Costs [Member]
Regulatory Assets [Line Items]
Regulatory assets	470	450
Price Risk Management [Member]
Regulatory Assets [Line Items]
Regulatory assets	297	424
Undepreciated Conventional Electromechanical Meters [Member]
Regulatory Assets [Line Items]
Regulatory assets	260
Unamortized Loss, Net Of Gain, On Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory assets	168	181
Other Long-Term Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory assets	$ 284	$ 381