Summary Of Significant Accounting Policies (Capitalized Cost Of Utility Plant) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Public Utility, Property, Plant and Equipment [Line Items]
General	$ 1,960		$ 1,911
Held for future use	74		72
Construction work in progress	1,241		1,458
NET UTILITY PLANT	24,965		23,794
Electric Generation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Generation	400		396
Electric Transmission [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	2,654		2,284
Electric Distribution [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	13,805		13,191
Gas Transmission [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	3,858	[1]	3,535	[1]
Steam Plant [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Generation	1,651		1,617
General [Member]
Public Utility, Property, Plant and Equipment [Line Items]
General	$ 1,282		$ 1,241

[1] Primarily distribution.