Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 310	$ 331
Regulated Electric | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	256	254
Regulated Natural Gas | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	54	77
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	249	279
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	107	123
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	140	154
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	197	204
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	77	82
Retail | Regulated Electric | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	118	120
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	52	75
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	30	41
Retail | Regulated Natural Gas | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	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	57	48
Interchange | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	56	47
Interchange | 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	306	327
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	253	251
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	53	76
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