Debt and Preferred Equity Investments - Narrative (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) segment investment	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)
Preferred equity investment
Number of investments, nonperforming | investment	1
Carrying Value	$ 1,097,202,000		$ 1,076,542,000
Recorded investment, nonaccrual status	$ 27,700,000
Number of portfolio segments of financial receivables (segment) | segment	1		1
Additional amount of financing receivables included in other assets	$ 66,400,000		$ 66,200,000
Current period provision for loan loss	0	$ 2,800,000	20,693,000
Allowance for loan and lease losses, real estate	13,213,000		13,213,000	$ 1,750,000
3 - High Risk Assets - Loss more likely than not
Preferred equity investment
Recorded investment, nonaccrual status	2,500,000
Financing Receivables, Equal to Greater than 90 Days Past Due
Preferred equity investment
Recorded investment, past due	0		0
Cumulative Effect, Period of Adoption, Adjustment
Preferred equity investment
Allowance for loan and lease losses, real estate			0	$ 27,803,000
Total floating rate
Preferred equity investment
Carrying Value	359,233,000		$ 352,460,000
Total floating rate | Mortgage/Mezzanine Loan Due March 2020
Preferred equity investment
Carrying Value	$ 6,800,000