Mortgages, Loans Payable And Other Obligations (Summary Of Mortgages, Loans Payable And Other Obligations) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Mortgages, loans payable and other obligations	$ 746,191		$ 757,495
Loss from early extinguishment of debt	703
51 Imclone [Member]
Debt Instrument [Line Items]
Property Name	51 Imclone (b)	[1]
Lender	Wells Fargo CMBS	[1]
Effective Rate	8.39%	[1],[2]
Mortgages, loans payable and other obligations			3,878	[1]
6305 Ivy Lane [Member]
Debt Instrument [Line Items]
Property Name	6305 Ivy Lane (c)	[3]
Lender	RGA Reinsurance Company	[3]
Effective Rate	5.525%	[2],[3]
Mortgages, loans payable and other obligations			5,984	[3]
9200 Edmonston Road [Member]
Debt Instrument [Line Items]
Property Name	9200 Edmonston Road (d)	[4]
Lender	Principal Commercial Funding L.L.C.	[4]
Effective Rate	5.534%	[2],[4]
Mortgages, loans payable and other obligations	4,115	[4]	4,305	[4]
Loan maturity date	May 01, 2013	[4]
Percentage of leased property occupied	100.00%
Port Imperial South 4/5 [Member]
Debt Instrument [Line Items]
Property Name	Port Imperial South 4/5
Lender	Wells Fargo Bank N.A.
LIBOR	LIBOR+3.50	[2]
Spread over LIBOR	3.50%
Mortgages, loans payable and other obligations	36,950		34,889
Loan maturity date	Mar. 30, 2014
395 West Passaic [Member]
Debt Instrument [Line Items]
Property Name	395 West Passaic
Lender	State Farm Life Insurance Co.
Effective Rate	6.004%	[2]
Mortgages, loans payable and other obligations	9,719		10,231
Loan maturity date	May 01, 2014
6301 Ivy Lane [Member]
Debt Instrument [Line Items]
Property Name	6301 Ivy Lane
Lender	RGA Reinsurance Company
Effective Rate	5.52%	[2]
Mortgages, loans payable and other obligations	5,447		5,667
Loan maturity date	Jul. 01, 2014
35 Waterview Boulevard [Member]
Debt Instrument [Line Items]
Property Name	35 Waterview Boulevard
Lender	Wells Fargo CMBS
Effective Rate	6.348%	[2]
Mortgages, loans payable and other obligations	18,417		18,746
Loan maturity date	Aug. 11, 2014
6 Becker, 85 Livingston, 75 Livingston And 20 Waterview [Member]
Debt Instrument [Line Items]
Property Name	6 Becker, 85 Livingston, 75 Livingston & 20 Waterview	[5],[6]
Lender	Wells Fargo CMBS	[5],[6]
Effective Rate	10.22%	[2],[5],[6]
Mortgages, loans payable and other obligations	64,233	[5],[6]	63,126	[5],[6]
Loan maturity date	Aug. 11, 2014	[5],[6]
Number of properties used to collateralize mortgage	4
4 Sylvan [Member]
Debt Instrument [Line Items]
Property Name	4 Sylvan (e)	[5]
Lender	Wells Fargo CMBS	[5]
Effective Rate	10.19%	[2],[5]
Mortgages, loans payable and other obligations	14,538	[5]	14,485	[5]
Loan maturity date	Aug. 11, 2014	[5]
10 Independence [Member]
Debt Instrument [Line Items]
Property Name	10 Independence (e)	[5]
Lender	Wells Fargo CMBS	[5]
Effective Rate	12.44%	[2],[5]
Mortgages, loans payable and other obligations	16,638	[5]	16,251	[5]
Loan maturity date	Aug. 11, 2014	[5]
Port Imperial South [Member]
Debt Instrument [Line Items]
Property Name	Port Imperial South
Lender	Wells Fargo Bank N.A.
LIBOR	LIBOR+1.75	[2]
Spread over LIBOR	1.75%
Mortgages, loans payable and other obligations	43,278		42,168
Loan maturity date	Sep. 19, 2015
4 Becker [Member]
Debt Instrument [Line Items]
Property Name	4 Becker (e)	[5]
Lender	Wells Fargo CMBS	[5]
Effective Rate	9.55%	[2],[5]
Mortgages, loans payable and other obligations	38,820	[5]	38,274	[5]
Loan maturity date	May 11, 2016	[5]
5 Becker [Member]
Debt Instrument [Line Items]
Property Name	5 Becker (e) (g)	[5],[7]
Lender	Wells Fargo CMBS	[5],[7]
Effective Rate	12.83%	[2],[5],[7]
Mortgages, loans payable and other obligations	13,092	[5],[7]	12,507	[5],[7]
Loan maturity date	May 11, 2016	[5],[7]
210 Clay [Member]
Debt Instrument [Line Items]
Property Name	210 Clay (e)	[5]
Lender	Wells Fargo CMBS	[5]
Effective Rate	13.42%	[2],[5]
Mortgages, loans payable and other obligations	12,767	[5]	12,275	[5]
Loan maturity date	May 11, 2016	[5]
Various [Member]
Debt Instrument [Line Items]
Property Name	Various (h)	[8]
Lender	Prudential Insurance	[8]
Effective Rate	6.332%	[2],[8]
Mortgages, loans payable and other obligations	147,477	[8]	149,281	[8]
Loan maturity date	Jan. 15, 2017	[8]
Number of properties used to collateralize mortgage	7
23 Main Street [Member]
Debt Instrument [Line Items]
Property Name	23 Main Street
Lender	JPMorgan CMBS
Effective Rate	5.587%	[2]
Mortgages, loans payable and other obligations	29,843		30,395
Loan maturity date	Sep. 01, 2018
Harborside Plaza 5 [Member]
Debt Instrument [Line Items]
Property Name	Harborside Plaza 5
Lender	The Northwestern Mutual Life Insurance Co. & New York Life Insurance Co.
Effective Rate	6.842%	[2]
Mortgages, loans payable and other obligations	225,139		228,481
Loan maturity date	Nov. 01, 2018
223 Canoe Brook Road [Member]
Debt Instrument [Line Items]
Property Name	233 Canoe Brook Road
Lender	The Provident Bank
Effective Rate	4.375%	[2]
Mortgages, loans payable and other obligations	3,877		3,945
Loan maturity date	Feb. 01, 2019
100 Walnut Avenue [Member]
Debt Instrument [Line Items]
Property Name	100 Walnut Avenue
Lender	Guardian Life Insurance Co.
Effective Rate	7.311%	[2]
Mortgages, loans payable and other obligations	18,792		19,025
Loan maturity date	Feb. 01, 2019
One River Center [Member]
Debt Instrument [Line Items]
Property Name	One River Center (i)	[9]
Lender	Guardian Life Insurance Co.	[9]
Effective Rate	7.311%	[2],[9]
Mortgages, loans payable and other obligations	$ 43,049	[9]	$ 43,582	[9]
Loan maturity date	Feb. 01, 2019	[9]
Number of properties used to collateralize mortgage	3

[1] With the sale of the property on May 31, 2013, the mortgage was satisfied by the Company. The Company incurred $0.7 million in costs for the debt satisfaction, which was included in discontinued operations: loss from early extinguishment of debt for the year ended December 31, 2013.

[2] Reflects effective rate of debt, including deferred financing costs, comprised of the cost of terminated treasury lock agreements (if any), debt initiation costs, mark-to-market adjustment of acquired debt and other transaction costs, as applicable.

[3] On October 1, 2013, the Company repaid the mortgage loan at par, using available cash. The original maturity date was January 1, 2014.

[4] The lease with the tenant occupying 100 percent of the building expired on January 9, 2013 and the tenant continues to occupy the building on a month-to-month basis. The mortgage loan matured on May 1, 2013 and was not repaid. The Company received a notice of default from the lender on July 17, 2013. The Company has requested a modification of the loan terms and is also in discussions regarding a deed-in-lieu of foreclosure with the lender.

[5] As the Company estimated that the carrying values of these properties may not be recoverable over their anticipated holding periods, the Company recorded impairment charges on these properties. See Note 3: Real Estate Transactions - Impairments on Properties Held and Used.

[6] Mortgage is cross collateralized by the four properties.

[7] The cash flow from this property is insufficient to cover operating costs and debt service. Consequently, the Company notified the lender and suspended debt service payments in August 2013. The Company has begun discussions with the lender regarding a modification of loan terms and began remitting available cash flow to the lender effective August 2013.

[8] Mortgage is collateralized by seven properties. The Operating Partnership has agreed, subject to certain conditions, to guarantee repayment of a portion of the loan.

[9] Mortgage is collateralized by the three properties comprising One River Center.