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v3.21.2

Related Party Transactions - Additional Information (Detail) - Vornado | 1 Months Ended | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Nov. 01, 2021 USD ($) | Jun. 30, 2021 USD ($) | Sep. 30, 2021 USD ($) $ / ft² | Dec. 31, 2020 USD ($)
Related Party Transaction [Line Items] |  |  |  |
Management fee agreement value |  |  | $ 2,800,000 |
Payments for commissions |  | $ 300,000 |  |
Subsequent Event |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Payments for commissions | $ 750,000 |  |  |
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 |  |  | $ 344,000 |
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 |  |  | $ 1,291,000 | $ 114,000
Development fees |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Development fee as percentage of development costs |  |  | 6.00% |
Amounts due to related party |  |  | $ 109,000 | 557,000
Management, property management, cleaning, engineering and security fees |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Amounts due to related party |  |  | $ 692,000 | $ 845,000
Vornado | Alexander's Inc. |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Noncontrolling interest, ownership percentage by noncontrolling owners |  |  | 32.40% |

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