Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 260	$ 278	$ 591	$ 606
Regulated Electric | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	236	243	490	493
Regulated Natural Gas | Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	24	35	101	113
Retail
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	214	221	493	496
Retail | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81	85	204	208
Retail | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	131	134	285	284
Retail | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	4	4
Retail | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	192	188	396	387
Retail | Regulated Electric | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	68	67	150	148
Retail | Regulated Electric | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	122	119	242	235
Retail | Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2	2	4	4
Retail | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	33	97	109
Retail | Regulated Natural Gas | Residential
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	13	18	54	60
Retail | Regulated Natural Gas | C&I
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9	15	43	49
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	41	54	89	103
Interchange | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	41	53	88	101
Interchange | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1	1	2
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	255	275	582	599
Total revenue from contracts with customers | Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	233	241	484	488
Total revenue from contracts with customers | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	22	34	98	111
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	5	3	9	7
Alternative revenue and other | Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	3	2	6	5
Alternative revenue and other | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	$ 2	$ 1	$ 3	$ 2