v3.26.1
Revenue - Disaggregation of Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation of Revenue [Line Items]        
Alternative revenue programs $ 15 $ 12 $ 38 $ 4
Total operating revenues 413 411 983 1,028
Residential Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 119 116 288 288
Commercial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 107 100 215 209
Industrial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 31 35 67 70
Public Street and Highway Lighting Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 3 3 5 5
Retail Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 260 254 575 572
Transmission Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 9 7 17 16
Other Electric Revenues from Contracts With Customers [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 2 6 6 14
Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 271 267 598 602
Avista Utilities [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 335 330 798 856
Derivative revenues 42 52 75 113
Alternative revenue programs 15 12 38 4
Deferrals and amortizations for rate refunds to customers (1) (2) (4) (2)
Other utility revenues 10 8 49 33
Total utility revenues 401 400 956 1,004
Avista Utilities [Member] | Residential Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 114 111 275 276
Avista Utilities [Member] | Commercial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 100 94 201 197
Avista Utilities [Member] | Industrial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 31 35 67 70
Avista Utilities [Member] | Public Street and Highway Lighting Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 3 3 5 5
Avista Utilities [Member] | Retail Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 248 243 548 548
Avista Utilities [Member] | Transmission Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 9 7 17 16
Avista Utilities [Member] | Other Electric Revenues from Contracts With Customers [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 2 6 6 14
Avista Utilities [Member] | Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 259 256 571 578
Avista Utilities [Member] | Residential Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 45 45 146 174
Avista Utilities [Member] | Commercial Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 22 22 65 87
Avista Utilities [Member] | Industrial and Interruptible Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 4 3 7 7
Avista Utilities [Member] | Retail Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 71 70 218 268
Avista Utilities [Member] | Transportation Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 3 1 4 6
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 2 3 5 4
Avista Utilities [Member] | Natural Gas [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer including assessed tax 76 74 227 278
Alaska Electric Light & Power [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 12 11 27 24
Alaska Electric Light & Power [Member] | Residential Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 5 5 13 12
Alaska Electric Light & Power [Member] | Commercial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 7 6 14 12
Alaska Electric Light & Power [Member] | Industrial Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 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
Alaska Electric Light & Power [Member] | Retail Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 12 11 27 24
Alaska Electric Light & Power [Member] | Transmission Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers 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
Alaska Electric Light & Power [Member] | Electric [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from contracts with customers $ 12 $ 11 $ 27 $ 24