Mortgages Payable - Schedule of Long -term Debt Instruments (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2024	Dec. 31, 2023
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Notes payable	$ 987,978	$ 1,092,551
Mortgages
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Notes payable, gross	996,544	1,096,544
Deferred debt issuance costs, net of accumulated amortization of $6,589 and $17,639, respectively	(8,566)	(3,993)
Deferred debt issuance costs, accumulated amortization	$ 6,589	17,639
Mortgages \| 731 Lexington Avenue \| Office Space
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest rate	5.04%
Notes payable, gross	$ 400,000	500,000
Mortgages \| 731 Lexington Avenue \| Retail Space
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest rate	1.76%
Notes payable, gross	$ 300,000	300,000
Rate	1.51%
Swapped fixed rate	1.76%
Mortgages \| Rego Park II \| Retail Space
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest rate	5.60%
Notes payable, gross	$ 202,544	202,544
Mortgages \| Rego Park II \| Retail Space \| SOFR
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Rate	1.45%
Mortgages \| Rego Park II \| Retail Space \| SOFR capped rate
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Rate	4.15%
Mortgages \| The Alexander apartment tower \| Apartment tower
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest rate	2.63%
Notes payable, gross	$ 94,000	$ 94,000

Notes payable gross.

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- References

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-SubTopic 310
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Amount of accumulated amortization of debt issuance costs.

+ References

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

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Fixed interest rate that will be received or paid upon exercise of the interest rate swaption contract.

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Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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