Debt and Preferred Equity Investments - Rollforward of Total Allowance for Loan Loss Reserves (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2020 USD ($) loan	Dec. 31, 2020 USD ($) loan	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Loan loss reserve activity
Balance at beginning of year			$ 1,750	$ 5,750	$ 0
Current period provision for loan loss			20,693	0	6,839
Write-offs charged against allowance			(37,033)	(4,000)	(1,089)
Balance at end of year	$ 13,213	$ 13,213	13,213	1,750	5,750
Write-offs charged against allowance			$ 37,033	4,000	1,089
Number of financing receivables on non-accrual without allowance for loan loss | loan	1	1	1
Financing receivable on non-accrual without allowance	$ 225,200	$ 225,200	$ 225,200
Investments Sold In 2020
Loan loss reserve activity
Write-offs charged against allowance	(19,000)
Write-offs charged against allowance	$ 19,000
Cumulative Effect, Period of Adoption, Adjustment
Loan loss reserve activity
Balance at beginning of year			$ 27,803	0	0
Current period provision for loan loss		$ 14,600
Balance at end of year				$ 27,803	$ 0