v3.26.3
Revenue - Disaggregation of Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Disaggregation of Revenue [Line Items]        
Alternative revenue programs $ (1) $ (8) $ 37 $ (4)
Total operating revenues 421 403 1,404 1,431
Residential Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 140 136 428 424
Commercial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 116 112 331 321
Industrial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 34 38 101 108
Public Street and Highway Lighting Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 3 2 8 7
Retail Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 293 288 868 860
Transmission Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 9 7 26 23
Other Electric Revenues from Contracts With Customers [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 8 7 14 21
Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 310 302 908 904
Avista Utilities [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 355 344 1,153 1,200
Derivative revenues 40 53 115 166
Alternative revenue programs (1) (8) 37 (4)
Deferrals and amortizations for rate refunds to customers 2 0 (2) (2)
Other utility revenues 14 5 63 38
Total utility revenues 410 394 1,366 1,398
Avista Utilities [Member] | Residential Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 135 133 410 409
Avista Utilities [Member] | Commercial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 110 106 311 303
Avista Utilities [Member] | Industrial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 34 38 101 108
Avista Utilities [Member] | Public Street and Highway Lighting Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 3 2 8 7
Avista Utilities [Member] | Retail Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 282 279 830 827
Avista Utilities [Member] | Transmission Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 9 7 26 23
Avista Utilities [Member] | Other Electric Revenues from Contracts With Customers [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 8 7 14 21
Avista Utilities [Member] | Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 299 293 870 871
Avista Utilities [Member] | Residential Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 31 29 177 203
Avista Utilities [Member] | Commercial Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 17 14 82 101
Avista Utilities [Member] | Industrial and Interruptible Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 2 2 9 9
Avista Utilities [Member] | Retail Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 50 45 268 313
Avista Utilities [Member] | Transportation Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 3 3 7 9
Avista Utilities [Member] | Other Natural Gas Revenues from Contracts With Customers [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 3 3 8 7
Avista Utilities [Member] | Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 56 51 283 329
Alaska Electric Light & Power [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 11 9 38 33
Alaska Electric Light & Power [Member] | Residential Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 5 3 18 15
Alaska Electric Light & Power [Member] | Commercial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 6 6 20 18
Alaska Electric Light & Power [Member] | Industrial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 0 0 0 0
Alaska Electric Light & Power [Member] | Public Street and Highway Lighting Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 0 0 0 0
Alaska Electric Light & Power [Member] | Retail Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 11 9 38 33
Alaska Electric Light & Power [Member] | Transmission Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 0 0 0 0
Alaska Electric Light & Power [Member] | Other Electric Revenues from Contracts With Customers [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 0 0 0 0
Alaska Electric Light & Power [Member] | Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers $ 11 $ 9 $ 38 $ 33