Short-Term Borrowings - Additional Information (Details) - USD ($) |
9 Months Ended | ||
|---|---|---|---|
Sep. 30, 2026 |
Jun. 30, 2026 |
Dec. 31, 2025 |
|
| Avista Utilities [Member] | |||
| Short-term Debt [Line Items] | |||
| Line of credit facility, maximum borrowing capacity | $ 500,000,000 | ||
| Line of credit facility, expiration date | 2029-06 | ||
| Line of credit facility, covenant terms, maximum debt to equity ratio | 65.00% | ||
| Letters of credit outstanding | $ 5,000,000 | $ 5,000,000 | |
| Avista Utilities [Member] | Letter of Credit [Member] | |||
| Short-term Debt [Line Items] | |||
| Line of credit facility, increase date | 2026-06 | ||
| Principal amount | $ 65,000,000 | $ 50,000,000 | |
| Letters of credit outstanding | 8,000,000 | $ 14,000,000 | |
| Alaska Electric Light & Power [Member] | |||
| Short-term Debt [Line Items] | |||
| Line of credit facility, maximum borrowing capacity | $ 25,000,000 | ||
| Line of credit facility, expiration date | 2028-06 | ||
| Line of credit facility, covenant terms, maximum debt to equity ratio | 67.50% |