Quarterly report pursuant to Section 13 or 15(d)

Recent Transactions (Dispositions) (Narrative) (Details)

v3.19.2
Recent Transactions (Dispositions) (Narrative) (Details) - Disposal Group, Not Discontinued Operations [Member] - USD ($)
6 Months Ended
Apr. 30, 2019
Jun. 30, 2019
Real Estate Properties [Line Items]    
Sales proceeds   $ 593,436,000
Malden, MA [Member]    
Real Estate Properties [Line Items]    
Sales proceeds $ 685,000  
Gain (Loss) on Disposition of Real Estate, Discontinued Operations $ 270,000