Debt and Preferred Equity Investments - Investment In Financing Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Carrying value	$ 1,052,110	$ 1,076,542
2021	64,515
2020	276,930
2019	310,326
Prior	400,339
1 - Low Risk Assets - Low probability of loss
Financing Receivable, Credit Quality Indicator [Line Items]
Carrying value	693,139	695,035
2021	64,515
2020	276,930
2019	57,230
Prior	294,464
2 - Watch List Assets - Higher potential for loss
Financing Receivable, Credit Quality Indicator [Line Items]
Carrying value	352,081	365,167
2021	0
2020	0
2019	253,096
Prior	98,985
3 - High Risk Assets - Loss more likely than not
Financing Receivable, Credit Quality Indicator [Line Items]
Carrying value	6,890	$ 16,340
2021	0
2020	0
2019	0
Prior	$ 6,890