Business Segments (Schedule of Revenue, By Products and Services) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 6,103	$ 6,940	$ 5,873	$ 6,163	$ 6,115	$ 6,628	$ 5,643	$ 6,135	$ 25,079	$ 24,521	$ 23,565
Electric Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									22,798	22,242	21,300
Gas Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									1,770	1,783	1,743
Commercial Renewables
Segment Reporting Information [Line Items]
Revenues									487	477	460
Total Reportable Segments
Segment Reporting Information [Line Items]
Revenues									25,055	24,502	23,503
Retail Electric
Segment Reporting Information [Line Items]
Revenues									19,745	19,013	18,177
Retail Electric | Electric Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									19,745	19,013	18,177
Wholesale Electric
Segment Reporting Information [Line Items]
Revenues									2,620	2,720	2,479
Wholesale Electric | Electric Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									2,231	2,345	2,104
Wholesale Electric | Commercial Renewables
Segment Reporting Information [Line Items]
Revenues									389	375	375
Retail Natural Gas
Segment Reporting Information [Line Items]
Revenues									1,782	1,817	1,732
Retail Natural Gas | Gas Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									1,782	1,817	1,732
Other
Segment Reporting Information [Line Items]
Revenues									1,037	1,081	1,239
Other | Electric Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									855	915	1,050
Other | Gas Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									84	64	104
Other | Commercial Renewables
Segment Reporting Information [Line Items]
Revenues									98	102	85
Operating Segments | Electric Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									22,831	22,273	21,331
Operating Segments | Gas Utilities and Infrastructure
Segment Reporting Information [Line Items]
Revenues									1,866	1,881	1,836
Operating Segments | Commercial Renewables
Segment Reporting Information [Line Items]
Revenues									487	477	460
Operating Segments | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenues									$ 25,184	$ 24,631	$ 23,627