Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 294	$ 274	$ 900	$ 810
Regulated Electric | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	274	252	767	700
Regulated Natural Gas | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	20	22	133	110
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	237	221	733	656
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	87	81	295	262
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	148	138	432	387
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	6	7
Retail | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	219	201	606	551
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	78	73	226	208
Retail | Regulated Electric | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	139	126	374	336
Retail | Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	6	7
Retail | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18	20	127	105
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	8	69	54
Retail | Regulated Natural Gas | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	12	58	51
Retail | Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Interchange
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	51	48	150	140
Interchange | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	51	48	150	140
Interchange | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	6	4
Other | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	0	3	0
Other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	2	3	4
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	290	271	889	800
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	271	249	759	691
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	19	22	130	109
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	4	3	11	10
Alternative revenue and other | Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	3	3	8	9
Alternative revenue and other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 1	$ 0	$ 3	$ 1