Related Party Transactions (Details)	1 Months Ended		12 Months Ended
	Dec. 22, 2014 USD ($)	Dec. 21, 2014 USD ($)	Dec. 31, 2016 USD ($) ft² $ / ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2016 USD ($)
Other Agreements
Property rentals			$ 151,444,000	$ 138,688,000	$ 136,628,000
Rego Park II | Retail space | Toys R Us/ Babies R Us
Other Agreements
Area of property (in square feet) | ft²			47,000
Property rentals			$ 2,675,000
Vornado
Related Party Transaction
Noncontrolling Interest, Ownership Percentage by Parent			32.40%
Management and Development Agreements
Management Fee Agreement Value (in US dollars)			$ 2,800,000
Vornado | Toys R Us/ Babies R Us
Other Agreements
Related Party's Ownership Interest In Tenants			32.50%
Vornado | Development fees
Management and Development Agreements
Development fee as percentage of development costs			6.00%
Other Agreements
Fees paid (in US dollars)			$ 54,000	5,795,000
Vornado | Development fees | Alexander apartment tower
Other Agreements
Fees paid (in US dollars)						$ 5,784,000
Vornado | Leasing Fees
Leasing Agreements
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%
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
Repayment of leasing costs (in US Dollars)	$ 40,353,000
Other Agreements
Fees paid (in US dollars)			$ 415,000	2,473,000
Vornado | Leasing Fees | LIBOR
Leasing Agreements
Debt Instrument, Description of Variable Rate Basis		one-year LIBOR
Basis spread over LIBOR		1.00%
Vornado | Property Management Fees | 731 Lexington Avenue | Office And Retail Space
Management and Development Agreements
Property Management Fee Agreement Price Per Square Foot | $ / ft²			0.5
Vornado | Property Management Fees | 731 Lexington Avenue | Common Area
Management and Development Agreements
Property Management Fee Agreement Value (in US dollars)			$ 297,000
Property Management Fee Escalation Percentage Per Annum			3.00%
Vornado | Property Management Fees | Rego Park II | Retail space
Management and Development Agreements
Property Management Fee Agreement Percentage Of Income			2.00%
Vornado | Management, property management, cleaning and security fees
Other Agreements
Fees paid (in US dollars)			$ 428,000	$ 283,000
Mr. Roth, Interstate, David Mandelbaum, and Russell B. Wight, Jr.
Related Party Transaction
Ownership Interest in the Company			26.30%
IP & Partners Through Vornado
Related Party Transaction
Ownership Interest in the Company			2.20%