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v3.20.1

Related Party Transactions - Additional Information (Detail) - Vornado | 3 Months Ended |
--- | --- | ---
Mar. 31, 2020 USD ($) $ / ft² | Dec. 31, 2019 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 | $ 324,000 |
Property management fee escalation percentage per annum | 3.00% |
Development fees |  |
Related Party Transaction [Line Items] |  |
Development fee as percentage of development costs | 6.00% |
Amounts due to related party | $ 215,000 | $ 68,000
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 | $ 50,000 | 563,000
Management, property management, cleaning, engineering and security fees |  |
Related Party Transaction [Line Items] |  |
Amounts due to related party | $ 705,000 | $ 795,000
Vornado | Alexander's Inc. |  |
Related Party Transaction [Line Items] |  |
Noncontrolling interest, ownership percentage by noncontrolling owners | 32.40% |

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