Debt and Preferred Equity Investments - Debt Investments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Mortgage loans on real estate, interest rate	5.80%
Debt Investments Held [Abstract]
Carrying value	$ 1,076,542,000	$ 1,580,306,000
Carrying value	1,076,542,000	1,580,306,000
Mezzanine Loan With Initial Maturity Date Of January 2021
Debt Investments Held [Abstract]
Amount participated out	66,600,000
Mezzanine Loan With Maturity June 2023
Debt Investments Held [Abstract]
Loan interest income	0
Mezzanine Loan with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Amount participated out	12,000,000.0
Loan interest income	0
Mezzanine Loan Due March 2022
Debt Investments Held [Abstract]
Amount participated out	400,000
Debt investment
Debt Investments Held [Abstract]
Future Funding Obligations	121,961,000
Senior Financing	4,526,287,000
Allowance for loan loss	(13,213,000)	0
Carrying value	816,756,000	1,341,070,000
Total fixed rate
Debt Investments Held [Abstract]
Future Funding Obligations	10,000,000
Senior Financing	2,777,272,000
Carrying value	477,509,000	499,410,000
Total fixed rate | Mezzanine Loan With Initial Maturity Date Of January 2021
Debt Investments Held [Abstract]
Future Funding Obligations	10,000,000
Senior Financing	67,000,000
Carrying value	32,888,000	0
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of September 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	15,000,000
Carrying value	3,500,000	3,500,000
Total fixed rate | Mortgage/Mezzanine Loan Due October 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	63,750,000
Carrying value	56,244,000	55,573,000
Total fixed rate | Mezzanine Loan With An Initial Maturity Of August 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	280,000,000
Carrying value	41,057,000	38,734,000
Total fixed rate | Mezzanine Loan With Maturity June 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	353,772,000
Carrying value	225,204,000	215,737,000
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	105,000,000
Carrying value	13,366,000	12,950,000
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 | Mezzanine Loan Repaid In 2020, 1
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	24,952,000
Total fixed rate | Mezzanine Loan Repaid In 2020, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	30,000,000
Total fixed rate | Mezzanine Loan Repaid In 2020, 3
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	12,714,000
Total floating rate
Debt Investments Held [Abstract]
Future Funding Obligations	111,961,000
Senior Financing	1,749,015,000
Carrying value	352,460,000	841,660,000
Total floating rate | Mezzanine Loan Repaid In 2020, 1
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	51,387,000
Total floating rate | Mezzanine Loan With An Initial Maturity Due April 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	275,000,000
Carrying value	49,956,000	49,809,000
Total floating rate | Jr Mortgage Participation/Mezzanine Loan with an Initial Maturity of July 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	60,000,000
Carrying value	15,733,000	15,698,000
Total floating rate | Mezzanine Loan With An Initial Maturity Due July 2021
Debt Investments Held [Abstract]
Future Funding Obligations	7,031,000
Senior Financing	172,809,000
Carrying value	35,318,000	41,395,000
Total floating rate | Mezzanine Loan Due July 2021, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	61,744,000
Carrying value	29,106,000	15,743,000
Total floating rate | Mezzanine Loan Due March 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,115,000,000
Carrying value	127,915,000	222,775,000
Total floating rate | Mortgage/Mezzanine Loan Due May 2022
Debt Investments Held [Abstract]
Future Funding Obligations	7,085,000
Senior Financing	0
Carrying value	60,532,000	0
Total floating rate | Mezzanine Loan Due December 2022
Debt Investments Held [Abstract]
Future Funding Obligations	44,000,000
Senior Financing	0
Carrying value	14,011,000	13,918,000
Total floating rate | Mezzanine Loan Due May 2023
Debt Investments Held [Abstract]
Future Funding Obligations	53,845,000
Senior Financing	64,462,000
Carrying value	19,889,000	69,839,000
Total floating rate | Mortgage/Mezzanine Loan Repaid In 2020, 1
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	35,386,000
Total floating rate | Junior Mortgage Repaid In 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	20,000,000
Total floating rate | Mortgage Loan Repaid In 2020, 1
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	19,971,000
Total floating rate | Mortgage Loan Repaid In 2020, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	106,473,000
Total floating rate | Mortgage/Mezzanine Loan Repaid In 2020, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	0	96,570,000
Total floating rate | Mortgage/Mezzanine Loan Repaid In 2020, 3
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying value	$ 0	$ 82,696,000