Regulatory Assets, Liabilities, And Balancing Accounts (Long-Term Regulatory Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 6,584	$ 6,322
Pension Benefits [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	2,304	2,347
Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	2,771	2,390
Utility Retained Generation [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	423	456
Environmental Compliance Costs [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	705	717
Price Risk Management [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	143	127
Electromechanical Meters [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	18	70
Unamortized Loss, Net Of Gain, On Reacquired Debt [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	98	113
Other Long Term Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 122	$ 102