| Document and Entity Information | Nov. 04, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 4, 2020 |
| Entity Registrant Name | AVISTA CORPORATION |
| Entity Central Index Key | 0000104918 |
| Entity Emerging Growth Company | false |
| Entity File Number | 1-3701 |
| Entity Incorporation, State or Country Code | WA |
| Entity Tax Identification Number | 91-0462470 |
| Entity Address, Address Line One | 1411 East Mission Avenue |
| Entity Address, City or Town | Spokane |
| Entity Address, State or Province | WA |
| Entity Address, Postal Zip Code | 99202-2600 |
| City Area Code | 509 |
| Local Phone Number | 489-0500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Information, Former Legal or Registered Name | None |
| Title of Each Class | Common Stock |
| Trading Symbols | AVA |
| Name of Each Exchange on Which Registered | NYSE |
