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Property, Plant And Equipment - Schedule of Major Classifications of Property, Plant And Equipment (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Public Utility, Property, Plant and Equipment [Line Items]    
Construction work-in-progress (CWIP) and other $ 238 $ 180
Total 8,418 7,979
Other Property 399 394
Total 8,424 7,985
Other Non-Reportable Segment Items [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Other Property 6 6
Avista Utilities [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Common Plant 760 760
Total 8,202 7,786
Avista Utilities [Member] | Electricity [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Production 1,523 1,498
Transmission 1,105 1,059
Distribution 2,580 2,383
Construction work-in-progress (CWIP) and other 452 395
Total 5,660 5,335
Avista Utilities [Member] | Natural Gas [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Natural gas underground storage 63 60
Distribution 1,624 1,539
Construction work-in-progress (CWIP) and other 95 92
Total 1,782 1,691
Alaska Electric Light & Power [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Common Plant 11 10
Total 216 193
Alaska Electric Light & Power [Member] | Electricity [Member]    
Public Utility, Property, Plant and Equipment [Line Items]    
Production 120 119
Transmission 23 23
Distribution 36 32
Construction work-in-progress (CWIP) and other 26 9
Total $ 205 $ 183