Revenues (Details) - Regulated Electric - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 522	$ 515
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	530	521
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	407	413
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	98	114
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	298	288
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	11
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	30	25
Transmission
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	84	76
Alternative and Other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	8	6
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1	$ 1