Related Party Transactions - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) $ / ft²	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	$ 10,729,000	$ 10,093,000	$ 11,331,000
Leasing Fees
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	1,213,000	1,378,000	$ 1,800,000
Vornado
Related Party Transaction [Line Items]
Other liabilities	715,000	801,000
Vornado | Management and Development Agreement
Related Party Transaction [Line Items]
Annual management fee	$ 2,800,000
Vornado | Management and Development Agreement | 731 Lexington Avenue | Office and Retail Space
Related Party Transaction [Line Items]
Property management fee agreement, price per square foot | $ / ft²	0.50
Vornado | Percentage of gross revenue | Rego Park II | Retail Site
Related Party Transaction [Line Items]
Property management fee, percent fee	2.00%
Vornado | Base management fee | 731 Lexington Avenue | Common Area
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	$ 365,000
Vornado | Escalating annualized management fee | 731 Lexington Avenue | Common Area
Related Party Transaction [Line Items]
Property management fee, percent fee	3.00%
Vornado | Development fee | 731 Lexington Avenue
Related Party Transaction [Line Items]
Property management fee, percent fee	6.00%
Vornado | 3% of rent for the first ten years
Related Party Transaction [Line Items]
Service fees, rate	3.00%
Vornado | 2% of rent for the eleventh through the twentieth year
Related Party Transaction [Line Items]
Service fees, rate	2.00%
Vornado | 1% of rent for the twenty-first through thirtieth year
Related Party Transaction [Line Items]
Service fees, rate	1.00%
Vornado | 1% increase in fee if third party is used
Related Party Transaction [Line Items]
Service fees, rate	1.00%
Vornado | 3% of gross proceeds used for commission for sales less than $50,000,000
Related Party Transaction [Line Items]
Related party transaction, rate	3.00%
Asset sale commission threshold	$ 50,000,000
Vornado | 1% of gross proceeds used for commission for sales greater than $50,000,000
Related Party Transaction [Line Items]
Related party transaction, rate	1.00%
Asset sale commission threshold	$ 50,000,000
Vornado | Management Property Management Cleaning Engineering and Security Fees
Related Party Transaction [Line Items]
Other liabilities	646,000	742,000
Vornado | Leasing Fees
Related Party Transaction [Line Items]
Other liabilities	$ 69,000	$ 59,000
Vornado | Alexander's Inc. | Vornado
Related Party Transaction [Line Items]
Parent ownership	32.40%
Director | Alexander's Inc. | Mr. Roth, Interstate, David Mandelbaum and Russell B, Wight, Jr.
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners	26.00%
Indirectly through Vornado | Alexander's Inc. | Directors indirect through Vornado
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners	2.30%