Supplementary Financial Information (Schedule Of Property, Plant And Equipment) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Supplementary Financial Information [Abstract]
Total assets in service	$ 18,735	$ 18,238
Less accumulated depreciation	6,332	6,125
Net of accumulated depreciation	12,403	12,113
Construction work in progress	359	335
Held for future use	15	15
Property, plant and equipment - net	$ 12,777	$ 12,463