Segment Information (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2022		Sep. 30, 2021		Sep. 30, 2022		Sep. 30, 2021
Segment Reporting Information [Line Items]
Net income	$ 40		$ 36		$ 102		$ 82
Regulated and Unregulated Operating Revenue	294		274		900	[1]	810	[1]
Affiliate Revenue	51		49		150		141
Natural gas	20		22		133		110
Total revenues
Segment Reporting Information [Line Items]
Regulated and Unregulated Operating Revenue	294	[2]	275	[2]	900		811
Intersegment Eliminations
Segment Reporting Information [Line Items]
Net income					0		(1)
Regulated and Unregulated Operating Revenue	0		(1)
Regulated Electric
Segment Reporting Information [Line Items]
Net income	42		38		89		77
Regulated Electric | Total revenues
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	274	[2]	252	[2]	767	[1]	700	[1]
Regulated Natural Gas
Segment Reporting Information [Line Items]
Net income	(3)		(4)		11		3
Revenues Including Intersegment Revenues	20		23		133		111
Regulated Natural Gas | Total revenues
Segment Reporting Information [Line Items]
Natural gas	20		22		133		110
Regulated Natural Gas | Intersegment Eliminations
Segment Reporting Information [Line Items]
Natural gas	0		1		0		1
All Other
Segment Reporting Information [Line Items]
Net income	$ 1		$ 2		$ 2		$ 2

[1] Total revenues include $150 million and $141 million of affiliate electric revenue for the nine months ended Sept. 30, 2022 and 2021, respectively

[2] Total revenues include $51 million and $49 million of affiliate electric revenue for the three months ended Sept. 30, 2022 and 2021, respectively.