Mortgages Payable - Summary of Outstanding Mortgages Payable (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Mortgage Loans on Real Estate
Deferred debt issuance costs, net of accumulated amortization of $16,071 and $14,551 respectively	$ (5,493)
Notes Payable (in US dollars)	$ 1,091,051	$ 1,089,613
LIBOR
Mortgage Loans on Real Estate
Interest cap rate	6.00%
Secured Overnight Financing Rate (SOFR)
Mortgage Loans on Real Estate
Interest cap rate	4.15%
Mortgages
Mortgage Loans on Real Estate
Notes payable, gross	$ 1,096,544	1,096,544
Deferred debt issuance costs, net of accumulated amortization of $16,071 and $14,551 respectively	(5,493)	(6,931)
Notes Payable (in US dollars)	1,091,051	1,089,613
Deferred debt issuance costs, accumulated amortization	$ 16,071	14,551
Mortgages \| 731 Lexington Avenue \| Office space
Mortgage Loans on Real Estate
Interest rate	5.22%
Notes payable, gross	$ 500,000	500,000
Mortgages \| 731 Lexington Avenue \| Office space \| LIBOR
Mortgage Loans on Real Estate
Basis spread over LIBOR or SOFR	0.90%
Mortgages \| 731 Lexington Avenue \| Office space \| LIBOR \| Maximum
Mortgage Loans on Real Estate
Interest cap rate	6.00%
Mortgages \| 731 Lexington Avenue \| Retail space
Mortgage Loans on Real Estate
Interest rate	1.76%
Notes payable, gross	$ 300,000	300,000
Mortgages \| 731 Lexington Avenue \| Retail space \| Secured Overnight Financing Rate (SOFR)
Mortgage Loans on Real Estate
Basis spread over LIBOR or SOFR	1.51%
Mortgages \| Rego Park II \| Retail space
Mortgage Loans on Real Estate
Interest rate	5.60%
Notes payable, gross	$ 202,544	202,544
Mortgages \| Rego Park II \| Retail space \| Secured Overnight Financing Rate (SOFR)
Mortgage Loans on Real Estate
Basis spread over LIBOR or SOFR	1.45%
Mortgages \| Rego Park II \| Retail space \| Secured Overnight Financing Rate (SOFR) \| Maximum
Mortgage Loans on Real Estate
Interest cap rate	4.15%
Mortgages \| The Alexander apartment tower \| Retail space
Mortgage Loans on Real Estate
Interest rate	2.63%
Notes payable, gross	$ 94,000	$ 94,000

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