XML 12 R1.htm IDEA: XBRL DOCUMENT v3.21.1
Document Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2020
Mar. 08, 2021
Jun. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2020    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Entity Registrant Name SMITH MIDLAND CORP    
Entity Central Index Key 0000924719    
Current Fiscal Year End Date --12-31    
Entity Filer Category Non-accelerated Filer    
Entity Emerging Growth Company false    
Entity Small Business true    
Entity Shell Company false    
Is Entity a Well-known Seasoned Issuer? No    
Is Entity a Voluntary Filer? No    
Is Entity's Reporting Status Current? Yes    
Entity Interactive Data Current Yes    
Entity Incorporation, State or Country Code DE    
Entity File Number 1-13752    
Entity Common Stock, Shares Outstanding   5,202,158  
Entity Public Float     $ 29,911,628