Mortgages and Other Loans Payable - Schedule of Mortgages and Other Loans Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Total fixed rate debt	$ 1,903,866	$ 1,587,474
Total floating rate debt	384,516	363,550
Total mortgages and other loans payable	2,288,382	1,951,024
Deferred financing costs, net of amortization	(8,287)	(6,389)
Total mortgages and other loans payable, net	2,280,095	1,944,635
7 Dey / 185 Broadway
Debt Instrument [Line Items]
Total fixed rate debt	190,148	190,148
10 East 53rd Street
Debt Instrument [Line Items]
Total fixed rate debt	204,663	205,000
100 Church Street
Debt Instrument [Line Items]
Total fixed rate debt	365,000	370,000
Landmark Square
Debt Instrument [Line Items]
Total fixed rate debt	100,000	100,000
315 W 33rd St
Debt Instrument [Line Items]
Total fixed rate debt	250,000	0
485 Lexington Avenue
Debt Instrument [Line Items]
Total fixed rate debt	450,000	450,000
500 Park Avenue
Debt Instrument [Line Items]
Total fixed rate debt	80,000	0
420 Lexington Avenue
Debt Instrument [Line Items]
Total fixed rate debt	264,055	272,326
100 Park Avenue
Debt Instrument [Line Items]
Total floating rate debt	382,872	360,000
Fund subscription line ⁽³⁾
Debt Instrument [Line Items]
Total floating rate debt	1,644	0
Maximum facility capacity	100,000
CMBS Repurchase Facility
Debt Instrument [Line Items]
Total floating rate debt	$ 0	$ 3,550
Weighted Average | 7 Dey / 185 Broadway
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	6.65%
Weighted Average | 10 East 53rd Street
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	5.37%
Weighted Average | 100 Church Street
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	5.89%
Weighted Average | Landmark Square
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.90%
Weighted Average | 315 W 33rd St
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.24%
Weighted Average | 485 Lexington Avenue
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.25%
Weighted Average | 500 Park Avenue
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	6.57%
Weighted Average | 420 Lexington Avenue
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	8.24%
Weighted Average | 100 Park Avenue
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.41%
Weighted Average | Fund subscription line ⁽³⁾
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.20%