Annual report pursuant to Section 13 and 15(d)

Recent Transactions (Dispositions/Rental Property Held for Sale, Net) (Narrative) (Details)

v3.6.0.2
Recent Transactions (Dispositions/Rental Property Held for Sale, Net) (Narrative) (Details)
$ in Thousands
 1 Months Ended 2 Months Ended 12 Months Ended
Sep. 30, 2015
Feb. 28, 2017
USD ($)
Dec. 31, 2016
USD ($)
ft²
item
property
Dec. 31, 2015
USD ($)
Real Estate Properties [Line Items]        
Unrealized losses on properties held for sale     $ (7,665)  
Sales proceeds     $ 664,481 $ 148,256
Multi-Family Properties [Member]        
Real Estate Properties [Line Items]        
Number of units | item     5,614  
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]        
Real Estate Properties [Line Items]        
Assets held for sale, Deferred charges and other assets     $ 1,700  
Assets held for sale, Unbilled rents receivable, net     1,200  
Assets held for sale, Accounts payable, accrued expenses and other liabilities     1,100  
Assets held for sale, Rents received in advance and security deposits     1,900  
Expected assets to be written off     2,900  
Expected liabilities to be written off     $ 500  
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Three Office Properties Disposed [Member] | Subsequent Event [Member]        
Real Estate Properties [Line Items]        
Sales proceeds   $ 45,800    
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Office [Member]        
Real Estate Properties [Line Items]        
Area of property (in square feet) | ft²     750,000  
Number of properties held for sale | property     8  
New Jersey Hudson River [Member]        
Real Estate Properties [Line Items]        
Strategic initiative period 3 years