XML 17 R1.htm IDEA: XBRL DOCUMENT v3.20.4
Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Mar. 01, 2021
Jun. 30, 2020
Document and Entity Information      
Entity Registrant Name ONE LIBERTY PROPERTIES, INC.    
Document Type 10-K    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2020    
Entity File Number 001-09279    
Entity Incorporation, State or Country Code MD    
Entity Tax Identification Number 13-3147497    
Entity Address, Address Line One 60 Cutter Mill Road    
Entity Address, City or Town Great Neck    
Entity Address, State or Province NY    
Entity Address, Postal Zip Code 11021    
City Area Code 516    
Local Phone Number 466-3100    
Title of 12(b) Security Common Stock    
Trading Symbol OLP    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Entity Shell Company false    
Entity Common Stock, Shares Outstanding   20,732,353  
Entity Public Float     $ 278
Entity Central Index Key 0000712770    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Amendment Flag false