Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Equity investments in unconsolidated subsidiaries	$ 160		$ 160		$ 155
Regulated Operating Revenue, Electric	2,941	$ 2,771	7,430	$ 7,345
Net income	603	527	1,185	1,080
Regulated Operating Revenue, Gas	219	222	1,082	1,324
Unregulated Operating Revenue	22	20	67	62
Regulated and Unregulated Operating Revenue	3,182	3,013	8,579	8,731
Equity Method Investments	160		160		155
Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Net income	632	550	1,148	1,032
Revenues Including Intersegment Revenues	2,942	2,771	7,431	7,346
Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Equity investments in unconsolidated subsidiaries	160		160		155
Net income	0	(1)	111	127
Revenues Including Intersegment Revenues			1,083	1,325
Equity Method Investments	160		160		$ 155
All Other
Segment Reporting Information [Line Items]
Net income	(29)	(22)	(74)	(79)
Operating Segments
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	3,183	3,013	8,581	8,733
Operating Segments | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	2,941	2,771	7,430	7,345
Operating Segments | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas	219	222	1,082	1,324
Operating Segments | All Other
Segment Reporting Information [Line Items]
Unregulated Operating Revenue	22	20	67	62
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	(1)	0	(2)	(2)
Intersegment Eliminations | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	$ 1	$ 0	1	1
Intersegment Eliminations | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas			$ 1	$ 1