Investments In Unconsolidated Joint Ventures (Summary Of Unconsolidated Joint Ventures) (Details) $ in Thousands					12 Months Ended
	Aug. 02, 2018 USD ($) item	Aug. 01, 2018 USD ($) item	Mar. 30, 2018 USD ($) item	Feb. 03, 2017	Dec. 31, 2018 USD ($) ft² item	Jan. 31, 2019 USD ($)	Dec. 11, 2018	Dec. 31, 2017 USD ($)	Feb. 15, 2017	Feb. 02, 2017	Dec. 31, 2016 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					1,317
Carrying Value					$ 232,750			$ 252,626
Balance					45,242			45,734
Mortgage loan face amount					$ 41,695
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %					20.00%
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %					85.00%
Marbella Tower Urban Renewal Associates LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item	412
Company's Effective Ownership %		24.27%
Balance	$ 131,000	$ 95,000
Property Debt, Maturity Date					Aug. 01, 2026
Property Debt, Interest Rate, Spread Over LIBOR	4.07%
Percentage of additional interest acquired	50.00%
PI North - Riverwalk C [Member] | Construction Loan [Member]
Schedule of Equity Method Investments [Line Items]
Maximum borrowing capacity					$ 112,000
Marbella II [Member] | Construction Loan [Member]
Schedule of Equity Method Investments [Line Items]
Number of extension options | item			4
Loan extension period			3 months
Extension fee			0.0625%
Maximum borrowing capacity			$ 75,000
Urby At Harborside [Member] | Construction/Permanent Loan [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %					85.00%
Maximum borrowing capacity					$ 192,000
PI North - Land [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					836
Residual ownership interest					20.00%
Plaza VIII & IX Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %										50.00%
Percentage of additional interest acquired				12.50%
The Shops At 40 Park Property [Member] | Metropolitan At 40 Park [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²					50,973
Balance					$ 6,100
Property Debt, Maturity Date					Sep. 01, 2019
Property Debt, Interest Rate, LIBOR					LIBOR+2.25
Property Debt, Interest Rate, Spread Over LIBOR					2.25%
Residual ownership interest					12.50%		25.00%
Lofts At 40 Park Property [Member] | Metropolitan At 40 Park [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					59
Indirect ownership interest					25.00%		50.00%
Number of stories | item					5
Lofts At 40 Park Property [Member] | Metropolitan At 40 Park [Member] | Construction Loan [Member]
Schedule of Equity Method Investments [Line Items]
Balance					$ 13,100
Property Debt, Maturity Date					Feb. 01, 2020
Property Debt, Interest Rate, Spread Over LIBOR					2.50%
Maximum borrowing capacity					$ 13,950
Metropolitan Property [Member] | Metropolitan At 40 Park [Member]
Schedule of Equity Method Investments [Line Items]
Balance					$ 36,000
Property Debt, Maturity Date					Sep. 01, 2020
Property Debt, Interest Rate					3.25%
Unconsolidated Joint Venture Multi-Family Properties [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					2,922
Unconsolidated Joint Venture Multi-Family Properties [Member] | Marbella RoseGarden, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					412
Company's Effective Ownership %					24.27%
Carrying Value								14,544
Unconsolidated Joint Venture Multi-Family Properties [Member] | Marbella Tower Urban Renewal Associates LLC [Member] | Subsequent Event [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %						50.00%
Balance						$ 117,000
Unconsolidated Joint Venture Multi-Family Properties [Member] | Metropolitan At 40 Park [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					130
Company's Effective Ownership %					25.00%
Carrying Value					$ 7,679			6,834
Balance					$ 55,227
Unconsolidated Joint Venture Multi-Family Properties [Member] | RiverTrace At Port Imperial [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					316
Company's Effective Ownership %					22.50%
Carrying Value					$ 8,112			8,864
Balance					$ 82,000
Property Debt, Maturity Date					Nov. 10, 2026
Property Debt, Interest Rate					3.21%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Crystal House [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					825
Company's Effective Ownership %					25.00%
Carrying Value					$ 29,570			30,570
Balance					$ 162,838
Property Debt, Maturity Date					Apr. 01, 2020
Property Debt, Interest Rate					3.17%
Number of units available for development | item					295
Number of approved units available for development | item					252
Unconsolidated Joint Venture Multi-Family Properties [Member] | PI North - Riverwalk C [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					360
Company's Effective Ownership %					40.00%
Carrying Value					$ 27,175			16,844
Property Debt, Maturity Date					Dec. 06, 2021
Property Debt, Interest Rate, LIBOR					L+2.75
Property Debt, Interest Rate, Spread Over LIBOR					2.75%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Marbella II [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					311
Company's Effective Ownership %					24.27%
Carrying Value					$ 15,414			16,471
Balance					$ 74,690
Property Debt, Maturity Date					Mar. 30, 2019
Property Debt, Interest Rate, LIBOR					L+2.25
Property Debt, Interest Rate, Spread Over LIBOR					2.25%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Marbella II [Member] | Subsequent Event [Member]
Schedule of Equity Method Investments [Line Items]
Balance						$ 117,000
Unconsolidated Joint Venture Multi-Family Properties [Member] | Riverpark At Harrison [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					141
Company's Effective Ownership %					45.00%
Carrying Value					$ 1,272			1,604
Balance					$ 29,819
Property Debt, Maturity Date					Aug. 01, 2025
Property Debt, Interest Rate					3.70%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Station House [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					378
Company's Effective Ownership %					50.00%
Carrying Value					$ 37,675			40,124
Balance					$ 98,504
Property Debt, Maturity Date					Jul. 01, 2033
Property Debt, Interest Rate					4.82%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Urby At Harborside [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					762
Company's Effective Ownership %					85.00%
Carrying Value					$ 85,317			94,429
Balance					$ 191,732
Property Debt, Maturity Date					Aug. 01, 2029
Property Debt, Interest Rate					5.197%
Unconsolidated Joint Venture Multi-Family Properties [Member] | PI North - Land [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					836
Company's Effective Ownership %					20.00%
Carrying Value					$ 1,678			1,678
Unconsolidated Joint Venture Multi-Family Properties [Member] | Liberty Landing [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					850
Company's Effective Ownership %					50.00%
Carrying Value					$ 337			337
Unconsolidated Joint Venture Multi-Family Properties [Member] | Hillsborough 206 [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²					160,000
Company's Effective Ownership %					50.00%
Carrying Value					$ 1,962			1,962
Unconsolidated Joint Venture Multi-Family Properties [Member] | Elmajo Urban Renewal Associates, LLC And Estuary Urban Renewal Associates, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %									7.50%
Unconsolidated Joint Venture Office Buildings [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²					500,000
Unconsolidated Joint Venture Office Buildings [Member] | Red Bank [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²					92,878
Company's Effective Ownership %					50.00%
Carrying Value					$ 3,127			4,602
Balance					$ 14,000
Property Debt, Maturity Date					Aug. 01, 2023
Property Debt, Interest Rate, LIBOR					L+2.25
Property Debt, Interest Rate, Spread Over LIBOR					2.25%
Number of extension options | item		2
Maximum borrowing capacity		$ 16,500
Unconsolidated Joint Venture Office Buildings [Member] | 12 Vreeland Road [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²					139,750
Company's Effective Ownership %					50.00%
Carrying Value					$ 7,019			6,734
Balance					$ 7,904
Property Debt, Maturity Date					Jul. 01, 2023
Property Debt, Interest Rate					2.87%
Unconsolidated Joint Venture Office Buildings [Member] | Offices At Crystal Lake [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²					106,345
Company's Effective Ownership %					31.25%
Carrying Value					$ 3,442			3,369
Balance					$ 4,076
Property Debt, Maturity Date					Nov. 01, 2023
Property Debt, Interest Rate					4.76%
Unconsolidated Joint Venture Other Property [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Value					$ 232,750			252,626
Balance					$ 820,790
Unconsolidated Joint Venture Other Property [Member] | Riverwalk Retail [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²					30,745
Company's Effective Ownership %					20.00%
Carrying Value					$ 1,539			1,625
Unconsolidated Joint Venture Other Property [Member] | Hyatt Regency Jersey City [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item					351
Company's Effective Ownership %					50.00%
Carrying Value					$ 112			440
Balance					$ 100,000
Property Debt, Maturity Date					Oct. 01, 2026
Property Debt, Interest Rate					3.668%
Unconsolidated Joint Venture Other Property [Member] | Other [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Value					$ 1,320			$ 1,595