Segment Information (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2021		Jun. 30, 2020		Jun. 30, 2021		Jun. 30, 2020
Segment Reporting Information [Line Items]
Net income		$ 134		$ 108		$ 301		$ 237
Unregulated Operating Revenue		9		10		22		23
Regulated and Unregulated Operating Revenue		1,174		911		2,335		1,968
Affiliate Revenue		1		1		2		2
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	[1]	1,174		911		2,335		1,968
Regulated Electric
Segment Reporting Information [Line Items]
Net income		107		89		188		163
Revenues Including Intersegment Revenues		827		715		1,560		1,427
Regulated Natural Gas
Segment Reporting Information [Line Items]
Net income		30		16		114		68
Revenues Including Intersegment Revenues		338		186		753		518
All Other
Segment Reporting Information [Line Items]
Net income		(3)		3		(1)		6
All Other | Total revenues
Segment Reporting Information [Line Items]
Unregulated Operating Revenue		$ 9	[2]	$ 10	[1]	$ 22	[1]	$ 23	[1]

[1] Total revenues include $1 million of other affiliate revenue for both the three months ended June 30, 2021 and 2020.

[2] Total revenues include $1 million of other affiliate revenue for both the three months ended June 30, 2021 and 2020.