Mortgages and Other Loans Payable (Details)	6 Months Ended
	Jun. 30, 2023 USD ($) extension	Dec. 31, 2022 USD ($)
Debt Instrument [Line Items]
Total fixed rate debt	$ 1,450,165,000	$ 3,165,814,000
Total floating rate debt	70,148,000	70,148,000
Total mortgages and other loans payable	1,520,313,000	3,235,962,000
Deferred financing costs, net of amortization	(6,907,000)	(8,399,000)
Total mortgages and other loans payable, net	1,513,406,000	3,227,563,000
Book value of collateral	1,900,000,000	3,800,000,000
719 Seventh Avenue
Debt Instrument [Line Items]
Total fixed rate debt	50,000,000	50,000,000
7 Dey / 185 Broadway
Debt Instrument [Line Items]
Total fixed rate debt	200,000,000	200,000,000
Total floating rate debt	10,148,000	10,148,000
420 Lexington Ave
Debt Instrument [Line Items]
Total fixed rate debt	280,165,000	283,064,000
100 Church Street
Debt Instrument [Line Items]
Total fixed rate debt	370,000,000	370,000,000
Landmark Square
Debt Instrument [Line Items]
Total fixed rate debt	100,000,000	100,000,000
485 Lexington Avenue
Debt Instrument [Line Items]
Total fixed rate debt	450,000,000	450,000,000
245 Park Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 0	1,712,750,000
Weighted Average | 719 Seventh Avenue
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.70%
Weighted Average | 7 Dey / 185 Broadway
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	7.59%
Interest rate, floating rate debt (as a percent)	2.85%
Weighted Average | 420 Lexington Ave
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.99%
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 | 485 Lexington Avenue
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.25%
Weighted Average | 245 Park Avenue
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)
Weighted Average | 690 Madison Avenue
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	0.50%
2017 Master Repurchase Agreement | 690 Madison Avenue
Debt Instrument [Line Items]
Total floating rate debt	$ 60,000,000	$ 60,000,000
Construction Loans | 7 Dey / 185 Broadway
Debt Instrument [Line Items]
Maximum facility capacity	$ 225,000,000
Term	3 years
Number of extension options | extension	2
Period of extension options	1 year