Debt and Preferred Equity Investments - Debt Investment (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Aggregate weighted average current yield (as a percent)	6.53%
Debt Investments Held [Abstract]
Carrying Value	$ 1,052,110,000	$ 1,076,542,000
Carrying Value	1,052,110,000	1,076,542,000
Mezzanine Loan Due June 2023
Debt Investments Held [Abstract]
Loan interest income	0
Mezzanine Loan Due June 2024
Debt Investments Held [Abstract]
Amount participated out	12,000,000
Loan interest income	0
Mezzanine Loan Due March 2022
Debt Investments Held [Abstract]
Amount participated out	400,000
Debt Investments in Mortgage Loans
Debt Investments Held [Abstract]
Future Funding Obligations	87,411,000
Senior Financing	4,637,210,000
Allowance for loan loss	(6,630,000)	(13,213,000)
Carrying Value	782,502,000	816,756,000
Total fixed rate
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	2,921,051,000
Carrying Value	507,637,000	477,509,000
Total fixed rate | Mortgage/Mezzanine Loan Due October 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	56,250,000	56,244,000
Total fixed rate | Mezzanine Loan Due August 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	280,000,000
Carrying Value	42,889,000	41,057,000
Total fixed rate | Mezzanine Loan Due June 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	370,642,000
Carrying Value	225,367,000	225,204,000
Total fixed rate | Mezzanine Loan Due June 2023, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	272,659,000
Carrying Value	64,515,000	0
Total fixed rate | Mezzanine Loan Due June 2024
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	105,000,000
Carrying Value	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
Senior Financing	95,000,000
Carrying Value	30,000,000	30,000,000
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of June 2027
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,712,750,000
Carrying Value	55,250,000	55,250,000
Total fixed rate | Mezzanine Loan With Initial Maturity Date Of December 2029
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	85,000,000
Carrying Value	20,000,000	20,000,000
Total fixed rate | Junior Mortgage Paid Off
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	32,888,000
Total fixed rate | Mezzanine Loan Paid Off
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	3,500,000
Total floating rate
Debt Investments Held [Abstract]
Future Funding Obligations	87,411,000
Senior Financing	1,716,159,000
Carrying Value	281,495,000	352,460,000
Total floating rate | Mezzanine Loan Due April 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	275,000,000
Carrying Value	49,996,000	49,956,000
Total floating rate | Mezzanine Loan Due July 2021, 2
Debt Investments Held [Abstract]
Future Funding Obligations	5,209,000
Senior Financing	179,763,000
Carrying Value	37,230,000	35,318,000
Total floating rate | Mezzanine Loan Due March 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,115,000,000
Carrying Value	132,249,000	127,915,000
Total floating rate | Mortgage/Mezzanine Loan Due May 2022
Debt Investments Held [Abstract]
Future Funding Obligations	4,268,000
Senior Financing	54,000,000
Carrying Value	7,697,000	6,958,000
Total floating rate | Mezzanine Loan Due December 2022
Debt Investments Held [Abstract]
Future Funding Obligations	30,437,000
Senior Financing	0
Carrying Value	27,729,000	14,011,000
Total floating rate | Mezzanine Loan Due May 2023
Debt Investments Held [Abstract]
Future Funding Obligations	47,497,000
Senior Financing	92,396,000
Carrying Value	26,594,000	19,889,000
Total floating rate | Junior Mortgage Participation/Mezzanine Loan Due July 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	15,733,000
Total floating rate | Mezzanine Loan Due July 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	29,106,000
Total floating rate | Mortgage Loan Paid Off
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	$ 0	$ 53,574,000