Related Party Transactions - Additional Information (Detail) - Vornado	3 Months Ended
Mar. 31, 2021 USD ($) $ / ft²	Dec. 31, 2020 USD ($)
Related Party Transaction [Line Items]
Management fee agreement value	$ 2,800,000
Property Management Fees \| Rego Park II \| Retail Space
Related Party Transaction [Line Items]
Property management fee agreement percentage of income	2.00%
Property Management Fees \| 731 Lexington Avenue \| Office and Retail Space
Related Party Transaction [Line Items]
Property management fee agreement, price per square foot \| $ / ft²	0.50
Property Management Fees \| 731 Lexington Avenue \| Common Area
Related Party Transaction [Line Items]
Property management fee agreement value	$ 334,000
Property management fee escalation percentage per annum	3.00%
Leasing fees
Related Party Transaction [Line Items]
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%
Percentage commissions on sale of assets under fifty million	3.00%
Asset sale commission threshold	$ 50,000,000
Percentage commissions on sale of assets over fifty million	1.00%
Amounts due to related party	$ 428,000	$ 114,000
Development fees
Related Party Transaction [Line Items]
Development fee as percentage of development costs	6.00%
Amounts due to related party	$ 33,000	557,000
Management, property management, cleaning, engineering and security fees
Related Party Transaction [Line Items]
Amounts due to related party	$ 951,000	$ 845,000
Vornado \| Alexander's Inc.
Related Party Transaction [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	32.40%

Asset sale commission threshold.

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Percentage of development costs that the related party will receive as per the Development agreement.

+ References

No definition available.

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- Definition

Percentage of rent payable to related party for leasing services for the eleventh through twentieth years of the lease.

+ References

No definition available.

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Percentage of rent payable to related party for leasing services for the first ten years of the lease.

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Percentage of rent payable to related party for leasing services for the twenty-first through thirtieth years of the lease.

+ References

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- Definition

The amount of management fee paid to related party to manage corporate activities.

+ References

No definition available.

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- Definition

Percentage of gross proceeds over $50,000,000 from the sale of any assets, payable to related party.

+ References

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Percentage of gross proceeds under $50,000,000 from the sale of any assets, payable to related party.

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- Definition

Percentage of increase in leasing services payable to related party if a real estate broker is used

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Property Management Fee Agreement, Price Per Square Foot

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Annual amount paid to related party as property management fees.

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Annual increase in the amount paid to related party as property management fees.

+ References

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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- Definition

The percentage charged for managing real estate properties.

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- Definition

Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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