Loans and Preferred Equity Held for Investment, net - Changes in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses at beginning of period		$ 272,624	$ 109,328	$ 517
Effect of CECL adoption			21,093	0	$ 0
Provision for loan losses		85,497	220,572	109,328
Charge-off		(41,160)	(46,693)	0
Recoveries		0	0	(517)
Transfer to loans held for sale(4)		(300,863)	(10,583)	0
Allowance for loan losses at end of period		37,191	272,624	109,328
Provision for loan losses transferred to held for sale	$ 5,200
Net impairment		2,700
Provision for loan losses		78,561	$ 220,572	$ 113,911
PD/LGD model
Allowance for Loan and Lease Losses [Roll Forward]
Unfunded commitments		800
Provision for loan losses		$ 37,200