| Document And Entity Information | Aug. 03, 2020 |
| Document Information [Line Items] | |
| Entity, Registrant Name | OTTER TAIL CORPORATION |
| Document, Type | 8-K |
| Document, Period End Date | Aug. 3, 2020 |
| Entity, Incorporation, State or Country Code | MN |
| Entity, File Number | 0-53713 |
| Entity, Tax Identification Number | 27-0383995 |
| Entity, Address, Address Line One | 215 South Cascade Street |
| Entity, Address, Address Line Two | P.O. Box 496 |
| Entity, Address, City or Town | Fergus Falls |
| Entity, Address, State or Province | MN |
| Entity, Address, Postal Zip Code | 56538-0496 |
| City Area Code | 866 |
| Local Phone Number | 410-8780 |
| Title of 12(b) Security | Common Shares |
| Trading Symbol | OTTR |
| Security Exchange Name | NASDAQ |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001466593 |
