Business Segments (Schedule of Revenue, By Products and Services) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 6,115	$ 6,628	$ 5,643	$ 6,135	$ 5,799	$ 6,482	$ 5,555	$ 5,729	$ 24,521	$ 23,565	$ 22,743
Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									22,242	21,300	21,336
Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									1,783	1,743	875
Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Revenues									477	460	484
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenues									24,502	23,503	22,695
Retail Electric [Member]
Segment Reporting Information [Line Items]
Revenues									19,013	18,177	18,338
Retail Electric [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									19,013	18,177	18,338
Wholesale Electric [Member]
Segment Reporting Information [Line Items]
Revenues									2,720	2,479	2,398
Wholesale Electric [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									2,345	2,104	2,095
Wholesale Electric [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Revenues									375	375	303
Retail Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues									1,817	1,732	871
Retail Natural Gas [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									1,817	1,732	871
Other Revenues [Member]
Segment Reporting Information [Line Items]
Revenues									1,081	1,239	1,144
Other Revenues [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									915	1,050	933
Other Revenues [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									64	104	30
Other Revenues [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Revenues									102	85	181
Operating Segments [Member] | Electric Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									22,273	21,331	21,366
Operating Segments [Member] | Gas Utilities and Infrastructure [Member]
Segment Reporting Information [Line Items]
Revenues									1,881	1,836	901
Operating Segments [Member] | Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Revenues									477	460	484
Operating Segments [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenues									$ 24,631	$ 23,627	$ 22,751