XML 14 R1.htm IDEA: XBRL DOCUMENT v3.19.2
Document and Entity Information - shares
 6 Months Ended
Jun. 30, 2019
Aug. 01, 2019
Document and Entity Information    
Entity Registrant Name ONE LIBERTY PROPERTIES INC  
Document Type 10-Q  
Document Period End Date Jun. 30, 2019  
Entity Current Reporting Status Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   19,883,529
Entity Central Index Key 0000712770  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Amendment Flag false