Quarterly report pursuant to Section 13 or 15(d)

Investments In Unconsolidated Joint Ventures (Narrative) (Details)

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Investments In Unconsolidated Joint Ventures (Narrative) (Details)
$ in Thousands, ft² in Millions
 3 Months Ended 9 Months Ended
Sep. 14, 2016
USD ($)
Sep. 13, 2016
USD ($)
Sep. 30, 2016
USD ($)
ft²
property
item
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
ft²
property
item
Dec. 31, 2015
USD ($)
Oct. 06, 2015
Schedule of Equity Method Investments [Line Items]              
Company's net investment in unconsolidated joint ventures     $ 319,807   $ 319,807 $ 303,457  
Amount outstanding     95,000   95,000 155,000  
Management, leasing, development and other services fees     900 $ 1,400      
Accounts receivable due from unconsolidated joint ventures     1,400   1,400 800  
Maximum exposure to loss     205,600   205,600    
Estimated future funding commitments     22,000   22,000    
Issuance of loan $ 17,800            
Accounts payable, accrued expenses and other liabilities     $ 185,326   $ 185,326 $ 135,057  
Unconsolidated Joint Venture Office Buildings [Member]              
Schedule of Equity Method Investments [Line Items]              
Number of properties | property     36   36    
Unconsolidated Joint Venture Office And Retail Buildings [Member]              
Schedule of Equity Method Investments [Line Items]              
Area of property (in square feet) | ft²     5.7   5.7    
Unconsolidated Joint Venture Retail Buildings [Member]              
Schedule of Equity Method Investments [Line Items]              
Number of properties | property     2   2    
Unconsolidated Joint Venture Multi-Family Properties [Member]              
Schedule of Equity Method Investments [Line Items]              
Number of properties | property     10   10    
Number of units | item     3,587   3,587    
Unconsolidated Joint Venture Hotel [Member]              
Schedule of Equity Method Investments [Line Items]              
Number of units | item     350   350    
Percentage of interest in venture             90.00%
Unconsolidated Joint Venture Development Projects [Member]              
Schedule of Equity Method Investments [Line Items]              
Number of units | item     822   822    
Unconsolidated Joint Venture Land Parcels [Member]              
Schedule of Equity Method Investments [Line Items]              
Number of units | item     4,151   4,151    
Unconsolidated Joint Ventures [Member] | Guarantee of Indebtedness of Others [Member]              
Schedule of Equity Method Investments [Line Items]              
Maximum borrowing capacity     $ 272,200   $ 272,200    
Amount outstanding     221,800   221,800    
Unconsolidated Joint Ventures [Member] | Parent Company [Member] | Guarantee of Indebtedness of Others [Member]              
Schedule of Equity Method Investments [Line Items]              
Maximum guaranteed amount     22,000   22,000    
Guaranteed amount     $ 22,000   $ 22,000    
Minimum [Member]              
Schedule of Equity Method Investments [Line Items]              
Percentage of interest in venture     7.50%   7.50%    
Maximum [Member]              
Schedule of Equity Method Investments [Line Items]              
Percentage of interest in venture     85.00%   85.00%    
Variable Interest Entity [Member]              
Schedule of Equity Method Investments [Line Items]              
Company's net investment in unconsolidated joint ventures     $ 183,600   $ 183,600    
Number of VIEs | property     4   4    
South Pier At Harborside [Member]              
Schedule of Equity Method Investments [Line Items]              
Letter of credit     $ 3,000   $ 3,000    
Property Debt, Balance   $ 59,100 $ 100,000   $ 100,000    
Property Debt, Interest Rate   6.15% 3.668%   3.668%    
Mortgage loan, maturity date   Nov. 01, 2016     Oct. 01, 2026    
Issuance of loan $ 35,700            
Accounts payable, accrued expenses and other liabilities     $ 3,317   $ 3,317