Mortgages and Other Loans Payable (Details)	1 Months Ended		9 Months Ended
	Oct. 31, 2022	Oct. 31, 2021	Sep. 30, 2022 USD ($) extension	Dec. 31, 2021 USD ($)	Apr. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)
Debt Instrument [Line Items]
Total fixed rate debt			$ 2,547,242,000	$ 1,073,409,000
Total floating rate debt			690,148,000	361,051,000
Total fixed rate and floating rate debt			3,237,390,000	1,434,460,000
Mortgages reclassed to liabilities related to assets held for sale			0	(34,537,000)
Total mortgages and other loans payable			3,237,390,000	1,399,923,000
Deferred financing costs, net of amortization			(8,374,000)	(5,537,000)
Total mortgages and other loans payable, net			3,229,016,000	1,394,386,000
Revolving credit facility, net			442,816,000	381,334,000
Book value of collateral			3,800,000,000	2,100,000,000
420 Lexington Ave
Debt Instrument [Line Items]
Total fixed rate debt			284,492,000	288,660,000
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			1,712,750,000	0
1080 Amsterdam Avenue
Debt Instrument [Line Items]
Total fixed rate debt			0	34,537,000
7 Dey / 185 Broadway
Debt Instrument [Line Items]
Total floating rate debt			210,148,000	198,169,000
719 Seventh Avenue
Debt Instrument [Line Items]
Total floating rate debt			50,000,000	50,000,000
690 Madison Avenue
Debt Instrument [Line Items]
Total floating rate debt			60,000,000	60,000,000
100 Church Street
Debt Instrument [Line Items]
Total fixed rate debt			0	200,212,000
Total floating rate debt			370,000,000	0
609 Fifth Avenue
Debt Instrument [Line Items]
Total floating rate debt			$ 0	52,882,000
Weighted Average | 420 Lexington Ave
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)			3.99%
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)			4.22%
Weighted Average | 7 Dey / 185 Broadway
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)			2.85%
Weighted Average | 719 Seventh Avenue
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)			1.20%
Weighted Average | 690 Madison Avenue
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)			1.50%
Weighted Average | 100 Church Street
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)			4.98%
2017 Master Repurchase Agreement
Debt Instrument [Line Items]
Total floating rate debt			$ 0	$ 0
Maximum facility capacity					$ 400,000,000	$ 300,000,000
Revolving credit facility, net			0
Construction Loans | 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	1 year
Construction Loans | Subsequent Event | 185 Broadway
Debt Instrument [Line Items]
Period of extension options	1 year