Goodwill And Other Intangibles (Schedule of Intangibles) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Purchases of Intangible Assets	$ 117	$ 99	$ 106
Intangible Assets	114	98
Power [Member]
Goodwill [Line Items]
Retirement of Intangibles	(100)	(100)
Purchases of Intangible Assets	117	99	106
Sales and Transfers of Intangible Assets	(1)	(2)
Impairment of Intangible Assets		(1)
Intangible Assets	114	98	102
Renewable Energy Credits [Member] | Power [Member]
Goodwill [Line Items]
Retirement of Intangibles	(93)	(94)
Purchases of Intangible Assets	90	99
Sales and Transfers of Intangible Assets	(1)	(1)
Impairment of Intangible Assets		0
Intangible Assets	40	44	40
Emissions Allowances [Member] | Power [Member]
Goodwill [Line Items]
Retirement of Intangibles	(7)	(6)
Purchases of Intangible Assets	27	0
Sales and Transfers of Intangible Assets	0	(1)
Impairment of Intangible Assets		(1)
Intangible Assets	$ 74	$ 54	$ 62