Regulatory Assets, Liabilities, And Balancing Accounts (Long-Term Regulatory Assets) (Details) - Entity [Domain] - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 6,476	$ 6,322
Pension Benefits [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	2,316	2,347
Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	2,649	2,390
Utility Retained Generation [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	434	456
Environmental Compliance Costs [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	686	717
Price Risk Management [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	142	127
Electromechanical Meters [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	36	70
Unamortized Loss, Net Of Gain, On Reacquired Debt [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	103	113
Other Long Term Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 110	$ 102