v3.26.3
Revenues (Details) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Total revenues        
Disaggregation of Revenue [Line Items]        
Total revenues $ 350,000,000 $ 310,000,000 $ 1,013,000,000 $ 914,000,000
Regulated Electric | Total revenues        
Disaggregation of Revenue [Line Items]        
Total revenues 330,000,000 291,000,000 885,000,000 803,000,000
Regulated Natural Gas | Total revenues        
Disaggregation of Revenue [Line Items]        
Total revenues 19,000,000 18,000,000 127,000,000 110,000,000
All Other | Total revenues        
Disaggregation of Revenue [Line Items]        
Total revenues 1,000,000 1,000,000 1,000,000 1,000,000
Retail        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 276,000,000 245,000,000 795,000,000 725,000,000
Retail | Residential        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 113,000,000 94,000,000 336,000,000 297,000,000
Retail | C&I        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 161,000,000 148,000,000 453,000,000 422,000,000
Retail | Other        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 2,000,000 3,000,000 6,000,000 6,000,000
Retail | Regulated Electric        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 258,000,000 227,000,000 675,000,000 619,000,000
Retail | Regulated Electric | Residential        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 103,000,000 86,000,000 268,000,000 238,000,000
Retail | Regulated Electric | C&I        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 153,000,000 139,000,000 401,000,000 376,000,000
Retail | Regulated Electric | Other        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 2,000,000 2,000,000 6,000,000 5,000,000
Retail | Regulated Natural Gas        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 17,000,000 17,000,000 119,000,000 105,000,000
Retail | Regulated Natural Gas | Residential        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 9,000,000 8,000,000 67,000,000 59,000,000
Retail | Regulated Natural Gas | C&I        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 8,000,000 9,000,000 52,000,000 46,000,000
Retail | Regulated Natural Gas | Other        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 0 0 0 0
Revenue from Contract with Customer, Excluding Assessed Tax 0      
Retail | All Other        
Disaggregation of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,000,000 1,000,000 1,000,000 1,000,000
Retail | All Other | Residential        
Disaggregation of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,000,000 0 1,000,000 0
Retail | All Other | C&I        
Disaggregation of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 0 0 0 0
Retail | All Other | Other        
Disaggregation of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax   1,000,000 0 1,000,000
Interchange        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 70,000,000 62,000,000 206,000,000 181,000,000
Interchange | Regulated Electric        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 69,000,000 61,000,000 201,000,000 177,000,000
Interchange | Regulated Natural Gas        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 1,000,000 1,000,000 5,000,000 4,000,000
Interchange | All Other        
Disaggregation of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 0 0 0 0
Total revenue from contracts with customers        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 346,000,000 307,000,000 1,001,000,000 906,000,000
Total revenue from contracts with customers | Regulated Electric        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 327,000,000 288,000,000 876,000,000 796,000,000
Total revenue from contracts with customers | Regulated Natural Gas        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 18,000,000 18,000,000 124,000,000 109,000,000
Total revenue from contracts with customers | All Other        
Disaggregation of Revenue [Line Items]        
Revenue from Contract with Customer, Excluding Assessed Tax 1,000,000 1,000,000 1,000,000 1,000,000
Alternative revenue and other        
Disaggregation of Revenue [Line Items]        
Alternative revenue and other 4,000,000 3,000,000 12,000,000 8,000,000
Alternative revenue and other | Regulated Electric        
Disaggregation of Revenue [Line Items]        
Alternative revenue and other 3,000,000 3,000,000 9,000,000 7,000,000
Alternative revenue and other | Regulated Natural Gas        
Disaggregation of Revenue [Line Items]        
Alternative revenue and other 1,000,000 0 3,000,000 1,000,000
Alternative revenue and other | All Other        
Disaggregation of Revenue [Line Items]        
Alternative revenue and other $ 0 $ 0 $ 0 $ 0