Real Estate Securities - Carrying Value of AFS Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Principal balance	$ 283,284	$ 304,077
Credit reserve	(44,967)	(32,940)
Unamortized discount, net	(95,718)	(124,255)
Amortized cost	142,599	146,882
Gross unrealized gains	77,294	92,481
Gross unrealized losses	(1,047)	(29)
CECL credit allowance	(388)	0
Carrying Value	218,458	239,334
Senior IO Securities
Debt Securities, Available-for-sale [Line Items]
Principal balance	0	26,331
Credit reserve	0	(533)
Unamortized discount, net	0	(10,427)
Amortized cost	0	15,371
Gross unrealized gains	0	10,450
Gross unrealized losses	0	(29)
CECL credit allowance	0
Carrying Value	0	25,792
Mezzanine
Debt Securities, Available-for-sale [Line Items]
Principal balance	2,000	13,512
Credit reserve	0	0
Unamortized discount, net	0	(527)
Amortized cost	2,000	12,985
Gross unrealized gains	14	702
Gross unrealized losses	0	0
CECL credit allowance	0
Carrying Value	2,014	13,687
Subordinate Securities
Debt Securities, Available-for-sale [Line Items]
Principal balance	281,284	264,234
Credit reserve	(44,967)	(32,407)
Unamortized discount, net	(95,718)	(113,301)
Amortized cost	140,599	118,526
Gross unrealized gains	77,280	81,329
Gross unrealized losses	(1,047)	0
CECL credit allowance	(388)
Carrying Value	$ 216,444	$ 199,855

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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