| Document and Entity Information | Apr. 29, 2020 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Apr. 29, 2020 |
| Entity Registrant Name | KADANT INC. |
| Entity File Number | 001-11406 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 52-1762325 |
| Entity Address, Address Line One | One Technology Park Drive |
| Entity Address, City or Town | Westford |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 01886 |
| City Area Code | 978 |
| Local Phone Number | 776-2000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $.01 par value |
| Trading Symbol | KAI |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000886346 |
| Amendment Flag | false |
