| Cover | Mar. 29, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Mar. 29, 2021 |
| Entity File Number | 1-16191 |
| Entity Registrant Name | TENNANT COMPANY |
| Entity Central Index Key | 0000097134 |
| Entity Tax Identification Number | 41-0572550 |
| Entity Incorporation, State or Country Code | MN |
| Entity Address, Address Line One | 701 North Lilac Drive, P.O. Box 1452 |
| Entity Address, City or Town | Minneapolis |
| Entity Address, State or Province | MN |
| Entity Address, Postal Zip Code | 55440 |
| 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, par value $0.375 per share |
| Trading Symbol | TNC |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
