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Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024
Disaggregation of Revenue [Line Items] |  |  |  |
Alternative revenue programs | $ 12 | $ 16 | $ 4 | $ 19
Total operating revenues | 411 | 402 | 1,028 | 1,011
Residential Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 116 | 98 | 288 | 247
Commercial Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 100 | 91 | 209 | 191
Industrial Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 35 | 30 | 70 | 58
Public Street and Highway Lighting Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 3 | 2 | 5 | 5
Retail Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 254 | 221 | 572 | 501
Transmission Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 7 | 10 | 16 | 19
Other Electric Revenues from Contracts With Customers [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 6 | 8 | 14 | 24
Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 267 | 239 | 602 | 544
Avista Utilities [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 330 | 319 | 856 | 819
Derivative revenues | 52 | 49 | 113 | 138
Alternative revenue programs | 12 | 16 | 4 | 19
Deferrals and amortizations for rate refunds to customers | (2) | 0 | (2) | 0
Other utility revenues | 8 | 7 | 33 | 10
Total utility revenues | 400 | 391 | 1,004 | 986
Avista Utilities [Member] | Residential Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 111 | 93 | 276 | 235
Avista Utilities [Member] | Commercial Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 94 | 85 | 197 | 178
Avista Utilities [Member] | Industrial Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 35 | 30 | 70 | 58
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 | 5 | 5
Avista Utilities [Member] | Retail Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 243 | 210 | 548 | 476
Avista Utilities [Member] | Transmission Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 7 | 10 | 16 | 19
Avista Utilities [Member] | Other Electric Revenues from Contracts With Customers [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 6 | 8 | 14 | 24
Avista Utilities [Member] | Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 256 | 228 | 578 | 519
Avista Utilities [Member] | Residential Natural Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 45 | 55 | 174 | 188
Avista Utilities [Member] | Commercial Natural Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 22 | 29 | 87 | 97
Avista Utilities [Member] | Industrial and Interruptible Natural Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 3 | 3 | 7 | 7
Avista Utilities [Member] | Retail Natural Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 70 | 87 | 268 | 292
Avista Utilities [Member] | Transportation Natural Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 1 | 3 | 6 | 5
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 | 1 | 4 | 3
Avista Utilities [Member] | Natural Gas [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contract with customer including assessed tax | 74 | 91 | 278 | 300
Alaska Electric Light & Power [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 11 | 11 | 24 | 25
Alaska Electric Light & Power [Member] | Residential Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 5 | 5 | 12 | 12
Alaska Electric Light & Power [Member] | Commercial Electric [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue from contracts with customers | 6 | 6 | 12 | 13
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 | 11 | 24 | 25
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 | $ 11 | $ 24 | $ 25

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