Regulatory Assets, Liabilities, And Balancing Accounts (Long-Term Regulatory Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 7,315	$ 7,029
Pension Benefits [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	2,415	2,414
Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	3,433	3,054
Utility Retained Generation [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	388	411
Environmental Compliance Costs [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	738	748
Price Risk Management [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	103	138
Unamortized Loss, Net Of Gain, On Reacquired Debt [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	85	94
Other Long Term Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 153	$ 170