Annual report pursuant to Section 13 and 15(d)

Recent Transactions (Unconsolidated Joint Venture Activity) (Narrative) (Details)

v3.10.0.1
Recent Transactions (Unconsolidated Joint Venture Activity) (Narrative) (Details)
$ in Thousands
12 Months Ended
Jan. 31, 2019
USD ($)
Dec. 11, 2018
USD ($)
Aug. 02, 2018
USD ($)
item
Sep. 29, 2017
USD ($)
Sep. 21, 2017
USD ($)
Feb. 15, 2017
USD ($)
Jan. 31, 2017
USD ($)
Dec. 31, 2018
USD ($)
ft²
item
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Aug. 01, 2018
USD ($)
Real Estate Properties [Line Items]                      
Gain (loss) on sale of investment in unconsolidated joint venture                 $ 23,131 $ 5,670  
Proceeds from the sale of investments in unconsolidated joint ventures                 98,599 6,420  
Investment in unconsolidated joint ventures               $ 11,789 36,060 35,930  
Debt               $ 2,792,651      
Number of units | item               1,317      
Purchase price of property               $ 168,398 90,068 121,582  
Mortgage loan               $ 45,242 $ 45,734  
Unconsolidated Joint Venture Multi-Family Properties [Member]                      
Real Estate Properties [Line Items]                      
Number of units | item               2,922      
Multi-Family Properties [Member]                      
Real Estate Properties [Line Items]                      
Number of units | item               6,910      
KP-MCG Curtis JV, LLC [Member]                      
Real Estate Properties [Line Items]                      
Gain (loss) on sale of investment in unconsolidated joint venture       $ 12,000              
Proceeds from the sale of investments in unconsolidated joint ventures       102,500              
Net sales proceeds held by qualified intermediary               $ 5,600      
Debt       $ 75,000              
KPG-P 100 IMW JV, LLC, Keystone-Penn And Keystone-Tristate [Member]                      
Real Estate Properties [Line Items]                      
Gain (loss) on sale of investment in unconsolidated joint venture             $ 7,400        
Proceeds from the sale of investments in unconsolidated joint ventures             $ 9,700        
Elmajo Urban Renewal Associates, LLC And Estuary Urban Renewal Associates, LLC [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]                      
Real Estate Properties [Line Items]                      
Gain (loss) on sale of investment in unconsolidated joint venture           $ 5,100          
Proceeds from the sale of investments in unconsolidated joint ventures           $ 5,100          
Percentage of interest in venture           7.50%          
RoseGarden Monaco, L.L.C. [Member]                      
Real Estate Properties [Line Items]                      
Gain (loss) on sale of investment in unconsolidated joint venture         $ (1,400)            
Metropolitan At 40 Park [Member]                      
Real Estate Properties [Line Items]                      
Purchase price of property   $ 1,300                  
Metropolitan At 40 Park [Member] | The Shops At 40 Park Property [Member]                      
Real Estate Properties [Line Items]                      
Area of property (in square feet) | ft²               50,973      
Residual ownership interest   25.00%           12.50%      
Mortgage loan               $ 6,100      
Metropolitan At 40 Park [Member] | Lofts At 40 Park Property [Member]                      
Real Estate Properties [Line Items]                      
Number of stories | item               5      
Number of units | item               59      
Indirect ownership interest   50.00%           25.00%      
Metropolitan At 40 Park [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]                      
Real Estate Properties [Line Items]                      
Percentage of interest in venture               25.00%      
Number of units | item               130      
Mortgage loan               $ 55,227      
Marbella II [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]                      
Real Estate Properties [Line Items]                      
Percentage of interest in venture               24.27%      
Number of units | item               311      
Mortgage loan               $ 74,690      
Marbella Tower Urban Renewal Associates LLC [Member]                      
Real Estate Properties [Line Items]                      
Percentage of interest in venture                     24.27%
Percentage of additional interest acquired     50.00%                
Number of units | item     412                
Purchase price of property     $ 65,600                
Repayment of mortgage loans     95,000                
Mortgage loan     $ 131,000               $ 95,000
Subsequent Event [Member] | Marbella II [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]                      
Real Estate Properties [Line Items]                      
Mortgage loan $ 117,000                    
Subsequent Event [Member] | Marbella Tower Urban Renewal Associates LLC [Member] | Unconsolidated Joint Venture Multi-Family Properties [Member]                      
Real Estate Properties [Line Items]                      
Percentage of interest in venture 50.00%                    
Purchase price of property $ 77,500                    
Repayment of mortgage loans 74,700                    
Mortgage loan $ 117,000