Debt and Preferred Equity Investments - Roll Forward of Net Book Balances (Details) - USD ($) $ in Thousands	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]
Document Period End Date	Dec. 31, 2020
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of period	$ 1,580,306	$ 2,099,393
Redemptions/sales/syndications/amortization	(1,048,643)	(1,190,689)
Net change in loan loss reserves	(11,463)	4,000
Balance at end of period	1,076,542	1,580,306
Debt investment
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/accretion	389,300	652,866
Preferred equity investments
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/accretion	$ 167,042	$ 14,736