Property, Plant and Equipment (Components of PP&E) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Electric generation, distribution assets and other	$ 25,242	$ 24,119
Accumulated depreciation	(8,227)	(7,942)
Property, Plant and Equipment, Net	17,015	16,177
Property Plant And Equipment Net Of Accumulated Depreciation Mortgaged Pledged Or Subject To Liens	11,000	10,000
Electric generation and distribution facilities
Property, Plant and Equipment [Line Items]
Electric generation, distribution assets and other	$ 22,875	21,529
Electric generation and distribution facilities | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Electric generation and distribution facilities | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	40 years
Other buildings
Property, Plant and Equipment [Line Items]
Electric generation, distribution assets and other	$ 1,651	1,971
Other buildings | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Other buildings | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	72 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Electric generation, distribution assets and other	$ 310	284
Furniture and Fixtures [Member] | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Furniture and Fixtures [Member] | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	25 years
Other
Property, Plant and Equipment [Line Items]
Electric generation, distribution assets and other	$ 406	$ 335
Other | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Other | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Life	44 years