Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Equity investments in unconsolidated subsidiaries	$ 155		$ 155		$ 155
Regulated Operating Revenue, Electric	2,286	$ 2,249	4,489	$ 4,574
Net income	287	238	582	553
Regulated Operating Revenue, Gas	280	308	863	1,102
Unregulated Operating Revenue	20	20	45	42
Regulated and Unregulated Operating Revenue	2,586	2,577	5,397	5,718
Equity Method Investments	155		155		155
Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Net income	289	249	516	482
Revenues Including Intersegment Revenues	2,287	2,250	4,490	4,575
Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Equity investments in unconsolidated subsidiaries	155		155		155
Net income	20	23	111	128
Revenues Including Intersegment Revenues			864	1,103
Equity Method Investments	155		155		$ 155
All Other
Segment Reporting Information [Line Items]
Net income	(22)	(34)	(45)	(57)
Operating Segments
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	2,587	2,578	5,399	5,720
Operating Segments | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	2,286	2,249	4,489	4,574
Operating Segments | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas	280	308	863	1,102
Operating Segments | All Other
Segment Reporting Information [Line Items]
Unregulated Operating Revenue	20	20	45	42
Intersegment Eliminations
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	(1)	(1)	(2)	(2)
Intersegment Eliminations | Electricity, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	$ 1	$ 1	1	1
Intersegment Eliminations | Natural Gas, US Regulated [Member]
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Gas			$ 1	$ 1