Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 331	$ 328
Regulated Electric | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	254	250
Regulated Natural Gas | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	77	78
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	279	275
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	123	123
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	154	150
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2
Retail | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	204	199
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	82	81
Retail | Regulated Electric | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	120	116
Retail | Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2
Retail | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	75	76
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	41	42
Retail | Regulated Natural Gas | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	34	34
Retail | Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Interchange
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	50	47
Interchange | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	50	47
Interchange | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(2)	2
Other | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(3)	1
Other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	1
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	327	324
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	251	247
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	76	77
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	4	4
Alternative revenue and other | Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	3	3
Alternative revenue and other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 1	$ 1