XML 18 R1.htm IDEA: XBRL DOCUMENT v3.20.4
Cover - USD ($)
 12 Months Ended
Dec. 31, 2020
Feb. 19, 2021
Jun. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2020    
Current Fiscal Year End Date --12-31    
Entity File Number 0-21220    
Entity Registrant Name ALAMO GROUP INC.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 74-1621248    
Entity Address, Address Line One 1627 East Walnut    
Entity Address, City or Town Seguin    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 78155    
City Area Code 830    
Local Phone Number 379-1480    
Title of 12(b) Security Common Stock, par value$.10 per share    
Trading Symbol ALG    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
ICFR Auditor Attestation Flag true    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 1,004,602,446
Entity Common Stock, Shares Outstanding   11,896,421  
Documents Incorporated by Reference Portions of the registrant’s proxy statement relating to the 2021 Annual Meeting of Stockholders have been incorporated by reference herein in response to Part III.    
Entity Central Index Key 0000897077    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Amendment Flag false