Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 1,091	$ 960	$ 967
Retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	898	788	785
Retail | Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	363	322	313
Retail | C&I
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	526	460	466
Retail | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	9	6	6
Interchange
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	189	168	177
Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4	4	5
Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Alternative revenue and other	14	14	14
Regulated Electric | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	910	843	833
Regulated Electric | Retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	721	675	655
Regulated Electric | Retail | Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	272	258	240
Regulated Electric | Retail | C&I
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	441	411	409
Regulated Electric | Retail | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	8	6	6
Regulated Electric | Interchange
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	189	168	177
Regulated Electric | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	1
Regulated Electric | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Alternative revenue and other	12	12	12
Regulated Natural Gas | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	180	117	134
Regulated Natural Gas | Retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	176	113	130
Regulated Natural Gas | Retail | Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	91	64	73
Regulated Natural Gas | Retail | C&I
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	85	49	57
Regulated Natural Gas | Retail | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Regulated Natural Gas | Interchange
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0
Regulated Natural Gas | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4	4	4
Regulated Natural Gas | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Alternative revenue and other	2	2	2
All Other | Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1
All Other | Retail
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1
All Other | Retail | Residential
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0
All Other | Retail | C&I
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0
All Other | Retail | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1
All Other | Interchange
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0
All Other | Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0
All Other | Alternative and Other [Member]
Disaggregation of Revenue [Line Items]
Alternative revenue and other	0
Total revenues
Disaggregation of Revenue [Line Items]
Total revenues	1,105	974	981
Total revenues | Regulated Electric
Disaggregation of Revenue [Line Items]
Total revenues	922	855	845
Total revenues | Regulated Natural Gas
Disaggregation of Revenue [Line Items]
Total revenues	182	$ 119	$ 136
Total revenues | All Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 1