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	$ 14	$ 12	$ 46	$ 46
Regulated and Unregulated Operating Revenue	255	218	536	475
Affiliate Revenue	46	41	92	82
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	255	218	536	475
Regulated Electric
Segment Reporting Information [Line Items]
Net income	16	16	40	41
Regulated Electric | Total revenues
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	224	199	448	411
Regulated Natural Gas
Segment Reporting Information [Line Items]
Net income	(2)	(3)	6	6
Revenues Including Intersegment Revenues	31	19	88	64
All Other
Segment Reporting Information [Line Items]
Net income	0	(1)	0	(1)
All Other | Total revenues
Segment Reporting Information [Line Items]
Other	$ 0	$ 0	$ 0	$ 0