XML 12 R1.htm IDEA: XBRL DOCUMENT v3.5.0.2
Document and Entity Information - shares
 9 Months Ended
Sep. 30, 2016
Oct. 21, 2016
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, 2016  
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   107,231,155
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q3