XML 33 R1.htm IDEA: XBRL DOCUMENT v3.3.0.814
Document and Entity Information - shares
 9 Months Ended
Sep. 30, 2015
Oct. 23, 2015
Document and Entity Information    
Entity Registrant Name FRANKLIN STREET PROPERTIES CORP /MA/  
Entity Central Index Key 0001031316  
Document Type 10-Q  
Document Period End Date Sep. 30, 2015  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   100,187,405
Document Fiscal Year Focus 2015  
Document Fiscal Period Focus Q3