Investments In Unconsolidated Joint Ventures (Summary Of Unconsolidated Joint Ventures) (Details)			9 Months Ended
	Sep. 01, 2021 USD ($)	Apr. 29, 2021 USD ($)	Sep. 30, 2021 USD ($) ft² item	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Carrying Value			$ 148,507,000		$ 162,382,000
Purchase price of property			$ 49,129,000	$ 123,797,000
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%
Construction Loan [Member]
Schedule of Equity Method Investments [Line Items]
Debt, Loan Extension Term			1 year
PI North - Riverwalk C [Member] | Construction Loan [Member]
Schedule of Equity Method Investments [Line Items]
Maximum borrowing capacity			$ 112,000,000
Percent of principal loan outstanding			10.00%
Riverpark At Harrison [Member]
Schedule of Equity Method Investments [Line Items]
Settlement Obligations			$ 500,000
PI North - Land [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item			771
Residual ownership interest			20.00%
12 Vreeland Road [Member]
Schedule of Equity Method Investments [Line Items]
Gain on sale		$ 2,000,000
Sale price		$ 2,000,000
Offices At Crystal Lake [Member]
Schedule of Equity Method Investments [Line Items]
Sale price	$ 1,900,000
The Shops At 40 Park Property [Member] | Metropolitan And Lofts At 40 Park [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²			50,973
Balance			$ 6,067,000
Property Debt, Interest Rate, Spread Over LIBOR			0.015%
Residual ownership interest			25.00%
Mortgage loan, maturity month and year			October 2022
Lofts At 40 Park Property [Member] | Metropolitan And Lofts At 40 Park [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item			59
Balance			$ 18,200,000
Property Debt, Interest Rate, Spread Over LIBOR			0.015%
Indirect ownership interest			50.00%
Number of stories | item			5
Mortgage loan, maturity month and year			January 2023
Metropolitan Property [Member] | Metropolitan And Lofts At 40 Park [Member]
Schedule of Equity Method Investments [Line Items]
Balance			$ 36,500,000
Property Debt, Interest Rate, Spread Over LIBOR			0.0285%
Mortgage loan, maturity month and year			October 2023
Unconsolidated Joint Venture Multi-Family Properties [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item			1,786
Unconsolidated Joint Venture Multi-Family Properties [Member] | Metropolitan And Lofts At 40 Park [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item			189
Company's Effective Ownership %			25.00%
Carrying Value			$ 2,688,000		3,347,000
Balance			$ 60,767,000
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			$ 6,139,000		6,667,000
Balance			$ 82,000,000
Property Debt, Maturity Date			Nov. 10, 2026
Property Debt, Interest Rate			3.21%
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			$ 36,709,000		36,992,000
Balance			$ 103,954,000
Property Debt, Maturity Date			Dec. 06, 2021
Property Debt, Interest Rate			2.75%
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			$ (521,000)		681,000
Balance			$ 30,192,000
Property Debt, Maturity Date			Jul. 01, 2035
Property Debt, Interest Rate			3.19%
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			$ 33,542,000		34,026,000
Balance			$ 93,789,000
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			$ 67,588,000		72,752,000
Balance			$ 191,805,000
Property Debt, Maturity Date			Aug. 01, 2029
Property Debt, Interest Rate			5.197%
Guaranteed amount			$ 22,000,000
Unconsolidated Joint Venture Multi-Family Properties [Member] | PI North - Land [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item			771
Company's Effective Ownership %			20.00%
Carrying Value			$ 1,678,000		1,678,000
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			$ 337,000		337,000
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					1,811,000
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					3,744,000
Gain on sale	(1,900,000)
Sale price	$ 1,900,000
Unconsolidated Joint Venture Other Property [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Value			$ 148,507,000		162,382,000
Balance			$ 662,507,000
Unconsolidated Joint Venture Other Property [Member] | Hyatt Regency Hotel Jersey City [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item			351
Company's Effective Ownership %			50.00%
Balance			$ 100,000,000
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			$ 347,000		$ 347,000