| Cover | Oct. 30, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Oct. 30, 2019 |
| Entity Registrant Name | Alamo Group Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 0-21220 |
| Entity Tax Identification Number | 74-1621248 |
| Entity Address, Address Line One | 1627 E. Walnut |
| Entity Address, City or Town | Seguin |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 78155 |
| City Area Code | 830 |
| Local Phone Number | 379-1480 |
| Title of 12(b) Security | Common Stock, par value$.10 per share |
| Trading Symbol | ALG |
| Security Exchange Name | NYSE |
| 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 | 0000897077 |
