Fair Value - Principal Amount, Carrying Value and Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financial assets:
Principal amount, financial assets	$ 2,149,018	$ 2,858,423
Financial liabilities:
Principal amount, financial liabilities	2,556,443	3,199,923
Future funding commitments	173,200	276,600
Carrying Value
Financial assets:
Loans and preferred equity held for investment, net	2,103,414	2,576,332
Fair Value
Financial assets:
Loans and preferred equity held for investment, net	2,109,093	2,470,561
Securitization bonds payable, net
Financial liabilities:
Principal amount, financial liabilities	840,423	840,423
Securitization bonds payable, net | Carrying Value
Financial liabilities:
Financial liabilities	834,621	833,153
Securitization bonds payable, net | Fair Value
Financial liabilities:
Financial liabilities	840,423	840,423
Mortgage and other notes payable, net
Financial liabilities:
Principal amount, financial liabilities	1,107,388	1,260,267
Mortgage and other notes payable, net | Carrying Value
Financial liabilities:
Financial liabilities	1,102,999	1,256,112
Mortgage and other notes payable, net | Fair Value
Financial liabilities:
Financial liabilities	1,107,388	1,260,675
Master repurchase facilities
Financial liabilities:
Principal amount, financial liabilities	608,632	1,099,233
Master repurchase facilities | Carrying Value
Financial liabilities:
Financial liabilities	608,632	1,099,233
Master repurchase facilities | Fair Value
Financial liabilities:
Financial liabilities	$ 608,632	$ 1,099,233