Relationship with Vornado (Details) - Vornado [Member]		3 Months Ended		9 Months Ended
	Dec. 22, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) $ / ft²	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Related Party Transaction [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent		32.40%		32.40%
Management and Development Agreements
Management Fee Agreement Value (in US dollars)				$ 2,800,000
Leasing Agreement [Abstract]
Asset Sale Commission Threshold (in US dollars)				$ 50,000,000
Percentage Commissions On Sale Of Assets Under Fifty Million				3.00%
Percentage Commissions On Sale Of Assets Over Fifty Million				1.00%
Leasing services fee and commission on asset sale, annual installment, maximum. (in US dollars)	$ 4,000,000
Debt Instrument, Description of Variable Rate Basis	One-year LIBOR
Basis spread over LIBOR	1.00%
Repayment of leasing costs (in US Dollars)	$ 40,353,000
Summary of fees to Vornado
Fees to related party (in US dollars)		$ 2,076,000	$ 4,337,000	$ 7,316,000	$ 8,561,000
Lexington Avenue Property [Member]
Other Agreements [Abstract]
Other Supervisory Fees				6.00%
Lexington Avenue Property [Member] | Office And Retail Space [Member]
Management and Development Agreements
Property Management Fee Agreement Price Per Square Foot | $ / ft²				0.5
Lexington Avenue Property [Member] | Common Area [Member]
Management and Development Agreements
Property Management Fee Agreement Value (in US dollars)				$ 280,000
Property Management Fee Escalation Percentage Per Annum				3.00%
Rego Park I [Member]
Other Agreements [Abstract]
Security Services Fee				6.00%
Rego Park II [Member]
Management and Development Agreements
Property Management Fee Agreement Percentage Of Income				2.00%
Other Agreements [Abstract]
Security Services Fee				6.00%
Company Management Fees [Member]
Summary of fees to Vornado
Fees to related party (in US dollars)		700,000	700,000	$ 2,100,000	2,100,000
Development fees [Member]
Management and Development Agreements
Development fee as percentage of development costs				6.00%
Summary of fees to Vornado
Fees to related party (in US dollars)		517,000	1,714,000	$ 2,176,000	2,463,000
Fees owed to Vornado (in US dollars)		5,540,000		$ 5,540,000		$ 3,394,000
Leasing Fees [Member]
Leasing Agreement [Abstract]
Lease Fee Percentage Of Rent One To Ten Years				3.00%
Lease Fee Percentage Of Rent Eleven To Twenty Years				2.00%
Lease Fee Percentage Of Rent Twenty First To Thirty Years				1.00%
Percentage Increase Lease Fee If Broker Used				1.00%
Summary of fees to Vornado
Fees to related party (in US dollars)		21,000	911,000	$ 419,000	1,275,000
Fees owed to Vornado (in US dollars)		15,000		15,000
Property Management Fees [Member]
Summary of fees to Vornado
Fees to related party (in US dollars)		838,000	$ 1,012,000	2,621,000	$ 2,723,000
Fees owed to Vornado (in US dollars)		$ 411,000		$ 411,000		$ 528,000