v3.26.1
Fair Value Measurements - Summary of Fair Value of Plan Assets by Level within Fair Value Hierarchy (Details) - EBP 003 - USD ($)
Dec. 31, 2025
Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value $ 955,258,640 $ 835,074,668
Avista Corp. Company Stock Fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 19,092,877 16,899,724
Self-Directed Securities    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 17,395,322 14,943,677
Mutual Funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 885,418,068 765,706,391
Collective Trust    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 33,352,373 37,524,876
Level 1    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 921,906,267 797,549,792
Level 1 | Avista Corp. Company Stock Fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 19,092,877 16,899,724
Level 1 | Self-Directed Securities    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 17,395,322 14,943,677
Level 1 | Mutual Funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 885,418,068 765,706,391
Level 1 | Collective Trust    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 0 0
Level 2    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 33,352,373 37,524,876
Level 2 | Avista Corp. Company Stock Fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 0 0
Level 2 | Self-Directed Securities    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 0 0
Level 2 | Mutual Funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 0 0
Level 2 | Collective Trust    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 33,352,373 37,524,876
Level 3    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 0 0
Level 3 | Avista Corp. Company Stock Fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 0 0
Level 3 | Self-Directed Securities    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 0 0
Level 3 | Mutual Funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value 0 0
Level 3 | Collective Trust    
EBP, Investment, Fair Value and NAV [Line Items]    
Total Investments at Fair Value $ 0 $ 0