Revenues (Details) - Regulated Electric - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 499	$ 471
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	508	477
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	380	327
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	101	97
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	267	222
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	8
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	45	69
Transmission
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	74	72
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	3
Alternative and Other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 9	$ 6