Mortgages Payable - Additional Information (Detail) - Mortgages	6 Months Ended
	Jun. 30, 2022
731 Lexington Avenue | Office Space
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Debt instrument, description of variable rate basis	LIBOR
Interest rate (in percentage)	2.22%
731 Lexington Avenue | Office Space | LIBOR
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Basis spread over LIBOR	0.90%
731 Lexington Avenue | Retail Space
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Debt instrument, description of variable rate basis	LIBOR
Interest rate (in percentage)	1.72%
731 Lexington Avenue | Retail Space | Interest rate derivatives (included in other assets)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest rate (in percentage)	1.72%
731 Lexington Avenue | Retail Space | LIBOR
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Basis spread over LIBOR	1.40%
Rego Park II | Retail Space
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Debt instrument, description of variable rate basis	LIBOR
Interest rate (in percentage)	3.02%
Rego Park II | Retail Space | LIBOR
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Basis spread over LIBOR	1.35%