Debt and Preferred Equity Investments - Debt Investment (Details) - USD ($)	8 Months Ended	9 Months Ended	38 Months Ended	39 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Aggregate weighted average current yield (as a percent)		9.15%
Debt Investments Held [Abstract]
Carrying Value, Fixed Rate	$ 334,327,000	$ 334,327,000	$ 334,327,000	$ 334,327,000	$ 623,280,000
Carrying Value	334,327,000	334,327,000	334,327,000	334,327,000	623,280,000
Allowance for loan loss	$ (13,520,000)	$ (13,520,000)	(13,520,000)	$ (13,520,000)	(6,630,000)	$ (6,630,000)
Loan interest income			$ 0
A Fund Affiliated With Winthrop Capital Partners | 625 Madison Avenue | Joint venture
Debt Investments Held [Abstract]
Ownership Interest	90.43%	90.43%	90.43%	90.43%
Debt Investments in Mortgage Loans
Debt Investments Held [Abstract]
Future Funding Obligations	$ 7,484,000	$ 7,484,000	$ 7,484,000	$ 7,484,000
Senior Financing	1,069,704,000	1,069,704,000	1,069,704,000	1,069,704,000
Carrying Value	208,430,000	208,430,000	208,430,000	208,430,000	503,422,000
Allowance for loan loss	(13,520,000)	(13,520,000)	(13,520,000)	(13,520,000)	(6,630,000)
Mezzanine Loan Due June 2024
Debt Investments Held [Abstract]
Amount participated out	12,000,000	12,000,000	12,000,000	12,000,000
Loan interest income				0
Total fixed rate
Debt Investments Held [Abstract]
Future Funding Obligations	0	0	0	0
Senior Financing	285,000,000	285,000,000	285,000,000	285,000,000
Carrying Value, Fixed Rate	63,366,000	63,366,000	63,366,000	63,366,000	365,842,000
Total fixed rate | Mezzanine Loan Due June 2024
Debt Investments Held [Abstract]
Future Funding Obligations	0	0	0	0
Senior Financing	105,000,000	105,000,000	105,000,000	105,000,000
Carrying Value, Fixed Rate	13,366,000	13,366,000	13,366,000	13,366,000	13,366,000
Total fixed rate | Mezzanine Loan, with an Initial Maturity Date of January 2025
Debt Investments Held [Abstract]
Future Funding Obligations	0	0	0	0
Senior Financing	95,000,000	95,000,000	95,000,000	95,000,000
Carrying Value, Fixed Rate	30,000,000	30,000,000	30,000,000	30,000,000	30,000,000
Total fixed rate | Mezzanine Loan With Initial Maturity Date of December 2029
Debt Investments Held [Abstract]
Future Funding Obligations	0	0	0	0
Senior Financing	85,000,000	85,000,000	85,000,000	85,000,000
Carrying Value, Fixed Rate	20,000,000	20,000,000	20,000,000	20,000,000	20,000,000
Total fixed rate | Mezzanine Loan Repaid
Debt Investments Held [Abstract]
Future Funding Obligations	0	0	0	0
Senior Financing	0	0	0	0
Carrying Value, Fixed Rate	0	0	0	0	225,367,000
Total fixed rate | Mezzanine Loan Repaid - 2
Debt Investments Held [Abstract]
Future Funding Obligations	0	0	0	0
Senior Financing	0	0	0	0
Carrying Value, Fixed Rate	0	0	0	0	77,109,000
Total floating rate
Debt Investments Held [Abstract]
Future Funding Obligations	7,484,000	7,484,000	7,484,000	7,484,000
Senior Financing	784,704,000	784,704,000	784,704,000	784,704,000
Carrying Value	158,584,000	158,584,000	158,584,000	158,584,000	144,210,000
Total floating rate | Mezzanine Loan Due April 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0	0	0	0
Senior Financing	275,000,000	275,000,000	275,000,000	275,000,000
Carrying Value	50,000,000	50,000,000	50,000,000	50,000,000	50,000,000
Loan interest income	0
Total floating rate | Mezzanine Loan Due November 2023
Debt Investments Held [Abstract]
Future Funding Obligations	3,761,000	3,761,000	3,761,000	3,761,000
Senior Financing	54,000,000	54,000,000	54,000,000	54,000,000
Carrying Value	8,243,000	8,243,000	8,243,000	8,243,000	8,243,000
Total floating rate | Mezzanine Loan Due May 2024
Debt Investments Held [Abstract]
Future Funding Obligations	3,723,000	3,723,000	3,723,000	3,723,000
Senior Financing	269,620,000	269,620,000	269,620,000	269,620,000
Carrying Value	61,258,000	61,258,000	61,258,000	61,258,000	46,884,000
Total floating rate | Mezzanine Loan Due January 2026
Debt Investments Held [Abstract]
Future Funding Obligations	0	0	0	0
Senior Financing	186,084,000	186,084,000	186,084,000	186,084,000
Carrying Value	$ 39,083,000	$ 39,083,000	$ 39,083,000	$ 39,083,000	$ 39,083,000