Quarterly report pursuant to Section 13 or 15(d)

Investments In Unconsolidated Joint Ventures (Recent Transactions) (Narrative) (Details)

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Investments In Unconsolidated Joint Ventures (Recent Transactions) (Narrative) (Details) (USD $)
6 Months Ended 6 Months Ended 6 Months Ended 0 Months Ended 6 Months Ended 6 Months Ended
Jun. 30, 2014
Dec. 31, 2013
Jun. 30, 2014
Harborside Unit A Urban Renewal, LLC [Member]
item
May 21, 2014
Harborside Unit A Urban Renewal, LLC [Member]
Jun. 30, 2014
Harborside Unit A Urban Renewal, LLC [Member]
Parent Company [Member]
Jun. 30, 2014
Harborside Unit A Urban Renewal, LLC [Member]
Ironstate Harborside-A, LLC [Member]
Jun. 30, 2014
KPG-MCG Curtis JV, LLC [Member]
sqft
Jun. 30, 2014
KPG-MCG Curtis JV, LLC [Member]
Parent Company [Member]
Jun. 30, 2014
KPG-MCG Curtis JV, LLC [Member]
Keystone Property Group [Member]
Jun. 06, 2014
90-Day Loan 1 [Member]
Keystone Property Group [Member]
Jun. 06, 2014
90-Day Loan 2 [Member]
Keystone Property Group [Member]
Jun. 30, 2014
Harborside Residential Project [Member]
Harborside Unit A Urban Renewal, LLC [Member]
item
Jun. 30, 2014
Harborside Residential Project [Member]
Harborside Unit A Urban Renewal, LLC [Member]
Parent Company [Member]
Jun. 30, 2014
Curtis Center Property [Member]
Parent Company [Member]
Jun. 30, 2014
Curtis Center Property [Member]
Keystone Property Group [Member]
Jun. 30, 2014
Curtis Center Property [Member]
KPG-MCG Curtis JV, LLC [Member]
Jun. 30, 2014
Curtis Center Property [Member]
KPG-MCG Curtis JV, LLC [Member]
Parent Company [Member]
Jun. 30, 2014
Curtis Center Property [Member]
KPG-MCG Curtis JV, LLC [Member]
Keystone Property Group [Member]
Jun. 30, 2014
Land [Member]
Harborside Unit A Urban Renewal, LLC [Member]
Parent Company [Member]
Schedule of Equity Method Investments [Line Items]                                      
Number of units     763                 763              
Total project costs                       $ 320,000,000 $ 88,000,000            
State tax credit                       33,000,000              
Percentage of interest in venture     85.00%                                
Investments in unconsolidated joint ventures 265,866,000 181,129,000 22,150,000 [1] 30,600,000   5,400,000 2,187,000 [1]                 125,000,000 62,500,000 62,500,000 5,500,000
Capital credit receivable per developable square foot     30                                
Aggregate capital credits             20,600,000                        
Percentage of operating return on capital         75.00% 25.00%                          
Internal rate of return         18.00%                            
Percentage of capital event cash flows distributed after initial internal rate of return reached         65.00% 35.00%                          
Percentage of interest in venture     85.00% [2]       50.00% [2] 50.00% 50.00%         50.00% 50.00%        
Area of property (in square feet)             885,000                        
Maturity period                   90 days 90 days                
Loan to affiliate 62,276,000                 52,300,000 10,000,000                
Interest rate                   3.50% 3.50%                
Lease period                               29 years      
Percentage of capital event cash flows distributed         75.00% 25.00%                          
Threshold of member unreturned capital for distribution of net operating cash flows             $ 0                        
Holding and distribution pattern under operating agreement     In general, the operating agreement of URL-Harborside provides that net operating cash flows are distributed first, to the members in respect of preferred return, as defined, until each member shall have received payment of the accrued and unpaid preferred return; and, thereafter, to each member as follows: 75 percent to the Company and 25 percent to ISA.                                
[1] See discussion in Recent Transactions following in this footnote.
[2] Company's effective ownership % represents the Company's entitlement to residual distributions after payments of priority returns, where applicable.