Real Estate Securities - Components of Carrying Value (Which Equals Fair Value) of Residential Available for Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Principal balance	$ 280,024	$ 304,077
Credit reserve	(37,717)	(32,940)
Unamortized discount, net	(109,538)	(124,255)
Amortized cost	132,769	146,882
Gross unrealized gains	22,315	92,481
Gross unrealized losses	(24,316)	(29)
Allowance for credit losses	(1,525)	0
Carrying Value	129,243	239,334
Senior
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)
Allowance for credit losses	0
Carrying Value	0	25,792
Mezzanine
Debt Securities, Available-for-sale [Line Items]
Principal balance	0	13,512
Credit reserve	0	0
Unamortized discount, net	0	(527)
Amortized cost	0	12,985
Gross unrealized gains	0	702
Gross unrealized losses	0	0
Allowance for credit losses	0
Carrying Value	0	13,687
Subordinate
Debt Securities, Available-for-sale [Line Items]
Principal balance	280,024	264,234
Credit reserve	(37,717)	(32,407)
Unamortized discount, net	(109,538)	(113,301)
Amortized cost	132,769	118,526
Gross unrealized gains	22,315	81,329
Gross unrealized losses	(24,316)	0
Allowance for credit losses	(1,525)
Carrying Value	$ 129,243	$ 199,855

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Debt Securities, Available For Sale, Unamortized Discounts Premiums

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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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Amount, before tax, of unrealized loss 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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Amount of allowance for credit loss 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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