Pension And Other Postretirement Benefits (Schedule Of Amounts Included In AOCL And Regulatory Assets) (Details) (USD $) In Millions, unless otherwise specified					12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011 Pension Benefits [Member]	Dec. 31, 2010 Pension Benefits [Member]	Dec. 31, 2011 Other Postretirement Benefits [Member]	Dec. 31, 2010 Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net actuarial loss					$ 822	$ 692	$ 247	$ 208
Unamortized prior service cost (credit)					11	(8)	(5)	(17)
Unamortized transition liability							1	2
Accumulated other comprehensive loss ($0 million and $17 million, net of tax, at December 31, 2011 and 2010, respectively)					39	29
Regulatory assets	2,196	1,915			794	655	243	193
Total					833	684	243	193
Accumulated other comprehensive loss, net of tax	$ (63)	$ (106)	$ (138)	$ (155)	$ 24	$ 17