Debt and Preferred Equity Investments - Schedule of Activity in Debt and Preferred Equity Investments (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2025 USD ($) investment	Dec. 31, 2024 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of period	$ 303,726	$ 346,745
Redemptions/sales/syndications/equity ownership/amortization	(148,168)	(64,629)
Net change in loan loss reserves	(300)	0
Balance at end of period	171,412	303,726
Debt and preferred equity investments	$ 171,412	303,726
Number of investments, nonperforming | investment	1
Preferred Equity | 625 Madison Avenue
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Debt and preferred equity investments	$ 118,300
Total floating rate
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Debt and preferred equity investments	131,080	117,160
Alternative Strategy Portfolio | Total floating rate
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Debt and preferred equity investments	53,500
Debt Investment
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/Accretion	13,921	12,890
Preferred Equity Investments
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/Accretion	$ 2,233	$ 8,720