Document and Entity Information Document (USD $)
12 Months Ended
Dec. 31, 2013
Mar. 03, 2014
Jun. 30, 2013
Document and Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2013    
Document Fiscal Year Focus 2013    
Document Fiscal Period Focus FY    
Entity Registrant Name KBS Legacy Partners Apartment REIT, Inc.    
Entity Central Index Key 0001469822    
Current Fiscal Year End Date --12-31    
Entity Filer Category Smaller Reporting Company    
Entity Common Stock, Shares Outstanding   19,576,838  
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Public Float     $ 0