Related Party Transactions - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) $ / ft²	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	$ 3,090,000	$ 2,247,000	$ 5,240,000	$ 5,537,000
Amounts due to Vornado	952,000		952,000		$ 801,000
Management And Development Agreement, Base Management Fee | 731 Lexington Avenue | Common Area
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction			$ 365,000
Leasing and Other Agreements, Percentage of Gross Proceeds Used for Commission for Sales Less Than Fifty Million
Related Party Transaction [Line Items]
Related party transaction, rate			3.00%
Asset sale commission threshold			$ 50,000,000
Leasing and Other Agreements, Percentage of Gross Proceeds Used For Commission for Sales Greater Than Fifty Million
Related Party Transaction [Line Items]
Related party transaction, rate			1.00%
Asset sale commission threshold			$ 50,000,000
Leasing fees
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction	129,000	$ 0	170,000	$ 1,318,000
Related Party | Rego Park III Land Parcel
Related Party Transaction [Line Items]
Payments for commissions	711,000
Related Party | Management and Development Agreement
Related Party Transaction [Line Items]
Annual management fee			$ 2,800,000
Related Party | 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
Related Party | Management and Development Agreement, Percentage of Gross Revenue | Rego Park II | Retail Space
Related Party Transaction [Line Items]
Property management fee agreement percentage of annual escalation			2.00%
Related Party | Management and Development Agreement, Annualized Management Fee | 731 Lexington Avenue | Common Area
Related Party Transaction [Line Items]
Property management fee agreement percentage of annual escalation			3.00%
Related Party | Management and Development Agreement, Development Fee
Related Party Transaction [Line Items]
Property management fee agreement percentage of annual escalation			6.00%
Related Party | Leasing and Other Agreements, Percentage of Rent for First Ten Years
Related Party Transaction [Line Items]
Service fees, rate			3.00%
Related Party | Leasing and Other Agreements, Percentage of Rent for Eleventh Through Twentieth Year
Related Party Transaction [Line Items]
Service fees, rate			2.00%
Related Party | Leasing and Other Agreements, Percentage of Rent for the Twenty-First Through the Thirtieth Year
Related Party Transaction [Line Items]
Service fees, rate			1.00%
Related Party | Leasing and Other Agreements, Percentage Increase in Fee if Third Party is Used
Related Party Transaction [Line Items]
Service fees, rate			1.00%
Related Party | Management, property management, cleaning, engineering and security fees
Related Party Transaction [Line Items]
Amounts due to Vornado	823,000		$ 823,000		742,000
Related Party | Leasing fees
Related Party Transaction [Line Items]
Amounts due to Vornado	$ 129,000		$ 129,000		$ 59,000
Vornado | Alexander's Inc. | Related Party
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners	32.40%		32.40%