Investments In Unconsolidated Joint Ventures (Summary Of Unconsolidated Joint Ventures) (Details)

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Investments In Unconsolidated Joint Ventures (Summary Of Unconsolidated Joint Ventures) (Details)							3 Months Ended	6 Months Ended	9 Months Ended
		Sep. 29, 2017 USD ($)	Sep. 21, 2017 USD ($)	Mar. 31, 2017 USD ($)	Feb. 15, 2017 USD ($)	Feb. 03, 2017 USD ($)	Sep. 30, 2017 USD ($) ft² item	Jun. 30, 2017 USD ($)	Sep. 30, 2017 USD ($) ft² item	Sep. 30, 2016 USD ($)	Apr. 30, 2017	Feb. 28, 2017 shares	Feb. 02, 2017	Dec. 31, 2016 USD ($)
Schedule of Equity Method Investments [Line Items]
Carrying Amount							$ 238,440,000		$ 238,440,000					$ 320,047,000
Cash consideration								$ 2,000,000
Accounts payable, accrued expenses and other liabilities							182,929,000		182,929,000					159,874,000
Purchase price of property									67,797,000	$ 94,017,000
Proceeds from the sale of investments in unconsolidated joint ventures									107,009,000	6,420,000
Debt							2,856,676,000		2,856,676,000					2,357,055,000
Gain (loss) on sale of investment in unconsolidated joint venture							$ 10,568,000		$ 23,131,000	$ 5,670,000
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %							12.50%		12.50%
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %							85.00%		85.00%
RoseGarden Monaco Holdings, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %												13.80%
Preferred units shares issued | shares												9,122
Percentage of interest in venture											100.00%
Crystal House Apartments Investors LLC [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of interest in developable land							50.00%		50.00%
Number of units available for development | item							295		295
Number of approved units available for development | item							252		252
RoseGarden Marbella South, L.L.C. [Member] | Construction Loan [Member]
Schedule of Equity Method Investments [Line Items]
Number of extension options | item									2
Loan extension period				1 year					1 year
Extension fee									0.25%
Maximum borrowing capacity				$ 75,000,000			$ 77,400,000		$ 77,400,000
Harborside Unit A Urban Renewal, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %							85.00%		85.00%
Harborside Unit A Urban Renewal, LLC [Member] | Construction/Permanent Loan [Member]
Schedule of Equity Method Investments [Line Items]
Maximum borrowing capacity							$ 192,000,000		$ 192,000,000
RoseGarden Monaco, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of investment in unconsolidated joint venture			$ (1,400,000)
Plaza VIII & IX Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Company's Effective Ownership %													50.00%
KPG-MCG Curtis JV, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from the sale of investments in unconsolidated joint ventures		$ 102,500,000
Debt		75,000,000
Gain (loss) on sale of investment in unconsolidated joint venture		$ 12,000,000
The Shops At 40 Park Property [Member] | Rosewood Morristown, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²							50,973		50,973
Property Debt, Balance							$ 6,213,000		$ 6,213,000
Property Debt, Maturity Date									Aug. 01, 2018
Property Debt, Interest Rate							3.63%		3.63%
Residual ownership interest							12.50%		12.50%
Lofts At 40 Park Property [Member] | Rosewood Morristown, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							59		59
Indirect ownership interest							25.00%		25.00%
Number of stories | item							5		5
Lofts At 40 Park Property [Member] | Rosewood Morristown, L.L.C. [Member] | Construction Loan [Member]
Schedule of Equity Method Investments [Line Items]
Property Debt, Balance						$ 6,337,000
Property Debt, Maturity Date						Feb. 01, 2020
Property Debt, Interest Rate, Spread Over LIBOR						2.50%
Metropolitan Property [Member] | Rosewood Morristown, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Property Debt, Balance							$ 37,044,000		$ 37,044,000
Property Debt, Maturity Date									Sep. 01, 2020
Property Debt, Interest Rate							3.25%		3.25%
Port Imperial North Land [Member] | Roseland/Port Imperial Partners, L.P. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							836		836
Residual ownership interest							20.00%		20.00%
Unconsolidated Joint Venture Multi-Family Properties [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							3,275		3,275
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		412
Company's Effective Ownership %	[1]						24.27%		24.27%
Carrying Amount							$ 14,738,000		$ 14,738,000					15,150,000
Property Debt, Balance							$ 95,000,000		$ 95,000,000
Property Debt, Maturity Date									May 01, 2018
Property Debt, Interest Rate							4.99%		4.99%
Unconsolidated Joint Venture Multi-Family Properties [Member] | RoseGarden Monaco Holdings, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item	[2]						523		523
Unconsolidated Joint Venture Multi-Family Properties [Member] | Rosewood Morristown, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item	[3],[4]						130		130
Company's Effective Ownership %	[1],[3],[4]						12.50%		12.50%
Carrying Amount	[3],[4]						$ 6,911,000		$ 6,911,000					7,145,000
Property Debt, Balance	[3],[4],[5]						$ 49,594,000		$ 49,594,000
Property Debt, Interest Rate	[3],[4]
Unconsolidated Joint Venture Multi-Family Properties [Member] | Riverwalk G Urban Renewal, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							316		316
Company's Effective Ownership %	[1]						22.50%		22.50%
Carrying Amount							$ 9,090,000		$ 9,090,000					9,707,000
Property Debt, Balance							$ 82,000,000		$ 82,000,000
Property Debt, Maturity Date									Nov. 10, 2026
Property Debt, Interest Rate							3.21%		3.21%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Elmajo Urban Renewal Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							355		355
Company's Effective Ownership %	[1]						7.50%		7.50%
Percentage of interest in venture					7.50%
Gain (loss) on sale of investment in unconsolidated joint venture					$ 5,100,000
Unconsolidated Joint Venture Multi-Family Properties [Member] | Crystal House Apartments Investors LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item	[6]						825		825
Company's Effective Ownership %	[1],[6]						25.00%		25.00%
Carrying Amount	[6]						$ 30,914,000		$ 30,914,000					30,565,000
Property Debt, Balance	[6]						$ 165,000,000		$ 165,000,000
Property Debt, Maturity Date	[6]								Apr. 01, 2020
Property Debt, Interest Rate	[6]						3.17%		3.17%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Roseland/Port Imperial Partners, L.P. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item	[3],[7]						360		360
Company's Effective Ownership %	[1],[3],[7]						20.00%		20.00%
Carrying Amount	[3],[7]						$ 2,311,000		$ 2,311,000					1,678,000
Unconsolidated Joint Venture Multi-Family Properties [Member] | RoseGarden Marbella South, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							311		311
Company's Effective Ownership %	[1]						24.27%		24.27%
Carrying Amount							$ 16,812,000		$ 16,812,000					18,050,000
Property Debt, Balance							$ 74,690,000		$ 74,690,000
Property Debt, Maturity Date									Mar. 30, 2018
Property Debt, Interest Rate, LIBOR	[8]								L+2.25
Property Debt, Interest Rate, Spread Over LIBOR	[8]								2.25%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Estuary Urban Renewal Unit B, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item	[9]						227		227
Company's Effective Ownership %	[1],[9]						7.50%		7.50%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Riverpark At Harrison I, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							141		141
Company's Effective Ownership %	[1]						45.00%		45.00%
Carrying Amount							$ 1,711,000		$ 1,711,000					2,085,000
Property Debt, Balance							$ 30,000,000		$ 30,000,000
Property Debt, Maturity Date									Aug. 01, 2025
Property Debt, Interest Rate							3.70%		3.70%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Capitol Place Mezz LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							378		378
Company's Effective Ownership %	[1]						50.00%		50.00%
Carrying Amount							$ 40,772,000		$ 40,772,000					43,073,000
Property Debt, Balance							$ 100,449,000		$ 100,449,000
Property Debt, Maturity Date									Jul. 01, 2033
Property Debt, Interest Rate							4.82%		4.82%
Unconsolidated Joint Venture Multi-Family Properties [Member] | Harborside Unit A Urban Renewal, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							762		762
Company's Effective Ownership %	[1]						85.00%		85.00%
Carrying Amount							$ 95,611,000		$ 95,611,000					100,188,000
Property Debt, Balance							$ 187,893,000		$ 187,893,000
Property Debt, Maturity Date									Aug. 01, 2029
Property Debt, Interest Rate	[10]						5.197%		5.197%
Unconsolidated Joint Venture Multi-Family Properties [Member] | RoseGarden Monaco, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item	[11]						250		250
Company's Effective Ownership %	[1],[11]						41.67%		41.67%
Carrying Amount	[11]													1,400,000
Unconsolidated Joint Venture Multi-Family Properties [Member] | Grand Jersey Waterfront URA, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							850		850
Company's Effective Ownership %	[1]						50.00%		50.00%
Carrying Amount							$ 337,000		$ 337,000					337,000
Unconsolidated Joint Venture Multi-Family Properties [Member] | Hillsborough 206 Holdings, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²							160,000		160,000
Company's Effective Ownership %	[1]						50.00%		50.00%
Carrying Amount							$ 1,962,000		$ 1,962,000					1,962,000
Unconsolidated Joint Venture Multi-Family Properties [Member] | Plaza VIII & IX Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²	[12]						1,225,000		1,225,000
Company's Effective Ownership %	[1],[12]						50.00%		50.00%
Carrying Amount	[12]													4,448,000
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]
Percentage of interest in venture					7.50%
Proceeds from the sale of investments in unconsolidated joint ventures					$ 5,100,000
Gain (loss) on sale of investment in unconsolidated joint venture					$ 5,100,000
Unconsolidated Joint Venture Office Buildings [Member] | Red Bank Corporate Plaza, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²							92,878		92,878
Company's Effective Ownership %	[1]						50.00%		50.00%
Carrying Amount							$ 4,669,000		$ 4,669,000					4,339,000
Property Debt, Balance							$ 14,026,000		$ 14,026,000
Property Debt, Maturity Date									May 17, 2018
Property Debt, Interest Rate, LIBOR									L+3.00
Property Debt, Interest Rate, Spread Over LIBOR									3.00%
Unconsolidated Joint Venture Office Buildings [Member] | 12 Vreeland Associates, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²							139,750		139,750
Company's Effective Ownership %	[1]						50.00%		50.00%
Carrying Amount							$ 6,554,000		$ 6,554,000					6,237,000
Property Debt, Balance							$ 9,885,000		$ 9,885,000
Property Debt, Maturity Date									Jul. 01, 2023
Property Debt, Interest Rate							2.87%		2.87%
Unconsolidated Joint Venture Office Buildings [Member] | BNES Associates III [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²							106,345		106,345
Company's Effective Ownership %	[1]						31.25%		31.25%
Carrying Amount							$ 3,199,000		$ 3,199,000					3,124,000
Property Debt, Balance							$ 4,969,000		$ 4,969,000
Property Debt, Maturity Date									Nov. 01, 2023
Property Debt, Interest Rate							4.76%		4.76%
Unconsolidated Joint Venture Office Buildings [Member] | KPG-P 100 IMW JV, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²	[13]						339,615		339,615
Unconsolidated Joint Venture Office Buildings [Member] | Keystone-Penn [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²	[13]						1,842,820		1,842,820
Company's Effective Ownership %	[1],[13]
Property Debt, Interest Rate, LIBOR	[13]								-
Unconsolidated Joint Venture Office Buildings [Member] | Keystone-TriState [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²	[13]						1,266,384		1,266,384
Company's Effective Ownership %	[1],[13]
Carrying Amount	[13]													2,285,000
Property Debt, Interest Rate	[13]
Unconsolidated Joint Venture Office Buildings [Member] | KPG-MCG Curtis JV, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²	[14]						885,000		885,000
Company's Effective Ownership %	[1],[14]						50.00%		50.00%
Carrying Amount	[14]													65,400,000
Property Debt, Balance	[14]
Property Debt, Interest Rate	[14]
Unconsolidated Joint Venture Other Property [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Amount							$ 238,440,000		$ 238,440,000					320,047,000
Property Debt, Balance							$ 912,617,000		$ 912,617,000
Unconsolidated Joint Venture Other Property [Member] | Roseland/North Retail, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Rentable Square Feet (sf) | ft²							30,745		30,745
Company's Effective Ownership %	[1]						20.00%		20.00%
Carrying Amount							$ 1,646,000		$ 1,646,000					1,706,000
Unconsolidated Joint Venture Other Property [Member] | South Pier At Harborside [Member]
Schedule of Equity Method Investments [Line Items]
Number of Apartment Units | item							350		350
Company's Effective Ownership %	[1]						50.00%		50.00%
Carrying Amount							$ 223,000		$ 223,000					163,000
Property Debt, Balance							$ 99,111,000		$ 99,111,000
Property Debt, Maturity Date									Oct. 01, 2026
Property Debt, Interest Rate							3.668%		3.668%
Unconsolidated Joint Venture Other Property [Member] | Other [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Amount	[15]						$ 980,000		$ 980,000					$ 1,005,000
[1] Company's effective ownership % represents the Company's entitlement to residual distributions after payments of priority returns, where applicable. [2] On February 28, 2017, 9,122 Series A-1 Units were issued to the joint venture partner as noncash consideration for the partner's approximate 13.8 percent ownership interest in the joint venture. In April 2017, the Company acquired the remaining joint venture interests and increased its ownership interest to 100 percent. See Note 3: Recent Transactions - Consolidation. [3] The Company's ownership interests in this venture are subordinate to its partner's preferred capital balance and the Company is not expected to meaningfully participate in the venture's cash flows in the near term. [4] Through the joint venture, the Company also owns a 12.5 percent interest in a 50,973 square feet retail building ("Shops at 40 Park") and a 25 percent interest in a to-be-built 59-unit, five story multi-family rental development property ("Lofts at 40 Park"). [5] Property debt balance consists of: (i) an amortizable loan, collateralized by the Metropolitan at 40 Park, with a balance of $37,044, bears interest at 3.25 percent, matures in September 2020; (ii) an amortizable loan, collateralized by the Shops at 40 Park, with a balance of $6,213, bears interest at 3.63 percent, matures in August 2018. On February 3, 2017, the venture obtained a construction loan for the Lofts at 40 Park with a balance of $6,337, which bears interest at LIBOR plus 250 basis points and matures in February 2020. [6] The Company also owns a 50 percent interest in a vacant land to accommodate the development of approximately 295 additional units of which 252 are currently approved. [7] The Company also owns a 20 percent residual interest in undeveloped land parcels: parcels 6, I, and J that can accommodate the development of 836 apartment units. [8] The construction loan had a maximum borrowing amount of $77,400 and provided, subject to certain conditions, two one-year extension options with a fee of 25 basis points for each year. On March 31, 2017, the Company exercised its first one-year extension option and concurrently the maximum borrowing amount was reduced to $75,000. [9] On February 15, 2017, the Company sold its 7.5 percent interest in Elmajo Urban Renewal Associates, LLC and Estuary Urban Renewal Unit B, LLC joint ventures that own operating multi-family properties, located in Weehawken, New Jersey for a combined sales price of $5.1 million. [10] The construction/permanent loan has a maximum borrowing amount of $192,000. The Company owns an 85 percent interest with shared control over major decisions such as, approval of budgets, property financings and leasing guidelines. The development project was placed in service in second quarter 2017. [11] On September 21, 2017, the joint venture agreement was terminated. Accordingly, the Company wrote off the carrying value of its investment in the joint venture and recorded a loss of $1.4 million on the disposition of its joint venture interest. [12] On February 3, 2017, the Company acquired the equity interest of its partner. See Note 3: Recent Transactions - Consolidation. [13] On January 31, 2017, the Company sold its equity interest in the joint venture. See Note 3: Recent Transactions - Unconsolidated Joint Venture Activity. [14] Includes undivided interests in the same manner as investments in noncontrolling partnership, pursuant to ASC 970-323-25-12. On September 29,2017, the Company sold its equity interest to its joint venture partner, which included the retirement of the Company's share in the debt of $75 million. See Note 3: Recent Transactions - Unconsolidated Joint Venture Activity. [15] The Company owns other interests in various unconsolidated joint ventures, including interests in assets previously owned and interest in ventures whose businesses are related to its core operations. These ventures are not expected to significantly impact the Company's operations in the near term.