| Document And Entity Information | May 04, 2021 |
| Document Information [Line Items] | |
| Entity, Registrant Name | TENNANT COMPANY |
| Document, Type | 8-K |
| Document, Period End Date | May 4, 2021 |
| Entity, Incorporation, State or Country Code | MN |
| Entity, File Number | 1-16191 |
| Entity, Tax Identification Number | 41-0572550 |
| Entity, Address, Address Line One | 10400 Clean Street |
| Entity, Address, City or Town | Eden Prairie |
| Entity, Address, State or Province | MN |
| Entity, Address, Postal Zip Code | 55344 |
| City Area Code | 763 |
| Local Phone Number | 540-1200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | TNC |
| Security Exchange Name | NYSE |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000097134 |
