Nuclear Decommissioning Trust Fund Investments (Fair Values Of Investments In Debt And Equity Securities In Nuclear Decommissioning Trust Fund) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	$ 316	$ 297
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	237	203
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4	6
Fair Value	549	494
Debt Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	175	157
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	7	4
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	1	2
Fair Value	182	159
Equity Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	138	137
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	230	199
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	4	4
Fair Value	364	332
Cash
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	1	3
Fair Value	1	3
Other Debt And Equity Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	2	1
Fair Value	$ 2	$ 1