v3.26.3
Information by Business Segments - Schedule of Business Segments (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Segment Reporting Information [Line Items]          
Operating revenues $ 421 $ 403 $ 1,404 $ 1,431  
Resource costs 132 115 465 501  
Other operating expenses 121 128 386 381  
Depreciation and amortization 75 73 210 216  
Interest income 5 4 11 9  
Interest expense 41 39 121 115  
Other segment expenses 24 22 77 80  
Income tax expense (benefit) 7 2 26 15  
Equity method earnings (losses) 23 1 46 (10)  
Net income (loss) 49 29 176 122  
Capital expenditures 185 133 511 379  
Total Assets 8,697   8,697   $ 8,359
Operating Segments [Member] | Utility Revenue [Member]          
Segment Reporting Information [Line Items]          
Operating revenues 421 403 1,404 1,431  
Resource costs 132 115 465 501  
Other operating expenses 121 125 385 377  
Depreciation and amortization 75 73 210 216  
Interest income 4 4 11 10  
Interest expense 40 40 120 115  
Other segment expenses 22 22 70 79  
Income tax expense (benefit) 2 2 18 18  
Equity method earnings (losses) 0 0 0 0  
Net income (loss) 33 30 147 135  
Capital expenditures 185 133 511 379  
Total Assets 8,503   8,503   8,206
Operating Segments [Member] | Avista Utilities [Member] | Utility Revenue [Member]          
Segment Reporting Information [Line Items]          
Operating revenues 410 394 1,366 1,398  
Resource costs 130 115 461 500  
Other operating expenses 116 120 371 364  
Depreciation and amortization 72 70 201 207  
Interest income 4 4 11 10  
Interest expense 39 38 116 110  
Other segment expenses 22 22 70 79  
Income tax expense (benefit) 2 3 16 17  
Equity method earnings (losses) 0 0 0 0  
Net income (loss) 33 30 142 131  
Capital expenditures 182 127 496 363  
Total Assets 8,210   8,210   7,917
Operating Segments [Member] | Alaska Electric Light & Power [Member] | Utility Revenue [Member]          
Segment Reporting Information [Line Items]          
Operating revenues 11 9 38 33  
Resource costs 2 0 4 1  
Other operating expenses 5 5 14 13  
Depreciation and amortization 3 3 9 9  
Interest income 0 0 0 0  
Interest expense 1 2 4 5  
Other segment expenses 0 0 0 0  
Income tax expense (benefit) 0 (1) 2 1  
Equity method earnings (losses) 0 0 0 0  
Net income (loss) 0 0 5 4  
Capital expenditures 3 6 15 16  
Total Assets 293   293   289
Other Non-Reportable Segment Items [Member] | Non-Utility Revenue [Member]          
Segment Reporting Information [Line Items]          
Operating revenues 0 0 0 0  
Resource costs 0 0 0 0  
Other operating expenses 0 3 1 4  
Depreciation and amortization 0 0 0 0  
Interest income 1 1 1 1  
Interest expense 1 0 2 2  
Other segment expenses 2 0 7 1  
Income tax expense (benefit) 5 0 8 (3)  
Equity method earnings (losses) 23 1 46 (10)  
Net income (loss) 16 (1) 29 (13)  
Capital expenditures 0 0 0 0  
Total Assets 220   220   177
Eliminations [Member]          
Segment Reporting Information [Line Items]          
Operating revenues 0 0 0 0  
Resource costs 0 0 0 0  
Other operating expenses 0 0 0 0  
Depreciation and amortization 0 0 0 0  
Interest income 0 (1) (1) (2)  
Interest expense 0 (1) (1) (2)  
Other segment expenses 0 0 0 0  
Income tax expense (benefit) 0 0 0 0  
Equity method earnings (losses) 0 0 0 0  
Net income (loss) 0 0 0 0  
Capital expenditures 0 $ 0 0 $ 0  
Total Assets $ (26)   $ (26)   $ (24)