Nuclear Decommissioning Trust Fund Investments (Fair Values Of Investments In Debt And Equity Securities In Nuclear Decommissioning Trust Fund) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost		$ 361	$ 341
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		256	226
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		10	11
Fair Value		607	556
Debt Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost		197	191
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		3	2
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax		4	4
Fair Value		196	189
Equity Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost		161	147
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		253	224
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax		6	7
Fair Value		408	364
Cash
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost		1	4
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		0	0
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax		0	0
Fair Value		1	4
Other Debt And Equity Securities
Nuclear Decommissioning Trust Fund Investments [Line Items]
Cost	[1]	2	1
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax		0	0
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax		0	0
Fair Value	[1]	$ 2	$ 1

[1] Represents net receivables and payables relating to pending security sales, interest, and security purchases.