v3.26.1
Information by Business Segments - Schedule of Business Segments (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Segment Reporting Information [Line Items]          
Operating revenues $ 413 $ 411 $ 983 $ 1,028  
Resource costs 127 130 333 386  
Other operating expenses 137 124 265 253  
Depreciation and amortization 68 72 135 143  
Interest income 2 3 6 5  
Interest expense 40 37 80 76  
Other segment expenses 23 28 53 58  
Income tax expense (benefit) 6 1 19 13  
Equity method earnings (losses) 21 (8) 23 (11)  
Net income (loss) 35 14 127 93  
Capital expenditures 176 143 326 246  
Total Assets 8,535   8,535   $ 8,359
Operating Segments [Member] | Utility Revenue [Member]          
Segment Reporting Information [Line Items]          
Operating revenues 413 411 983 1,028  
Resource costs 127 130 333 386  
Other operating expenses 136 124 264 252  
Depreciation and amortization 68 72 135 143  
Interest income 3 3 7 6  
Interest expense 41 36 80 75  
Other segment expenses 18 25 48 57  
Income tax expense (benefit) 3 3 16 16  
Equity method earnings (losses) 0 0 0 0  
Net income (loss) 23 24 114 105  
Capital expenditures 176 143 326 246  
Total Assets 8,368   8,368   8,206
Operating Segments [Member] | Avista Utilities [Member] | Utility Revenue [Member]          
Segment Reporting Information [Line Items]          
Operating revenues 401 400 956 1,004  
Resource costs 125 129 331 385  
Other operating expenses 132 120 255 244  
Depreciation and amortization 65 69 129 137  
Interest income 3 3 7 6  
Interest expense 40 35 77 72  
Other segment expenses 17 24 48 57  
Income tax expense (benefit) 3 3 14 14  
Equity method earnings (losses) 0 0 0 0  
Net income (loss) 22 23 109 101  
Capital expenditures 167 136 314 236  
Total Assets 8,076   8,076   7,917
Operating Segments [Member] | Alaska Electric Light & Power [Member] | Utility Revenue [Member]          
Segment Reporting Information [Line Items]          
Operating revenues 12 11 27 24  
Resource costs 2 1 2 1  
Other operating expenses 4 4 9 8  
Depreciation and amortization 3 3 6 6  
Interest income 0 0 0 0  
Interest expense 1 1 3 3  
Other segment expenses 1 1 0 0  
Income tax expense (benefit) 0 (0) 2 2  
Equity method earnings (losses) 0 0 0 0  
Net income (loss) 1 1 5 4  
Capital expenditures 9 7 12 10  
Total Assets 292   292   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 1 0 1 1  
Depreciation and amortization 0 0 0 0  
Interest income 0 0 0 0  
Interest expense 0 1 1 2  
Other segment expenses 5 3 5 1  
Income tax expense (benefit) 3 (2) 3 (3)  
Equity method earnings (losses) 21 (8) 23 (11)  
Net income (loss) 12 (10) 13 (12)  
Capital expenditures 0 0 0 0  
Total Assets 193   193   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 (1) (0) (1) (1)  
Interest expense (1) 0 (1) (1)  
Other segment expenses 0 0 0 0  
Income tax expense (benefit) 0 0 0 0  
Equity method earnings (losses) 0   0 0  
Net income (loss) 0 0 0 0  
Capital expenditures 0 $ 0 0 $ 0  
Total Assets $ (26)   $ (26)   $ (24)