Document And Entity Information - shares
 3 Months Ended
Mar. 31, 2021
May 12, 2021
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2021  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q1  
Entity Filer Category Non-accelerated Filer  
Entity Registrant Name ELECTRO SENSORS INC  
Entity Central Index Key 0000351789  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Small Business true  
Entity Common Stock, Shares Outstanding   3,395,521
Trading Symbol ELSE  
Entity Emerging Growth Company false  
Document Quarterly Report true  
Document Transition Report false  
Entity File Number 000-09587  
Entity Incorporation, State or Country Code MN  
Entity Tax Identification Number 41-0943459  
Entity Address, Address Line One 6111 Blue Circle Drive  
Entity Address, City or Town Minnetonka  
Entity Address, State or Province MN  
Entity Address, Postal Zip Code 55343-9108  
City Area Code 952  
Local Phone Number 930-0100  
Title of 12(b) Security Common stock  
Security Exchange Name NASDAQ  
Entity Interactive Data Current Yes  
Entity Shell Company false