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Residential Mortgage Securities and MSR Related Assets (Interest Income) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Interest income		$ 54,137	$ 274,554	$ 322,475
Agency MBS
Debt Securities, Available-for-sale [Line Items]
Coupon interest		14,038	82,446	88,233
Effective yield adjustment		(5,186)	(26,545)	(25,930)
Interest income		8,852	55,901	62,303
Legacy Non-Agency MBS
Debt Securities, Available-for-sale [Line Items]
Coupon interest		18,263	87,024	109,714
Effective yield adjustment		10,565	59,622	69,309
Interest income		28,828	146,646	179,023
Accretion income	$ 2,700		14,500
RPL/NPL MBS
Debt Securities, Available-for-sale [Line Items]
Coupon interest		8,376	53,086	46,339
Effective yield adjustment		560	338	1,434
Interest income		8,936	53,424	47,773
Accretion income	$ 1,400		329
CRT securities
Debt Securities, Available-for-sale [Line Items]
Coupon interest		7,010	20,532	30,628
Effective yield adjustment		511	(1,949)	2,748
Interest income		7,521	18,583	33,376
MSR related assets
Debt Securities, Available-for-sale [Line Items]
Coupon interest		25,970	52,644	27,174
Effective yield adjustment		9,987	3	1,246
Interest income		$ 35,957	$ 52,647	$ 28,420

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Accretion Income

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- Definition

Represents the coupon interest income derived from securities backed by a pool of mortgages or trust deeds.

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No definition available.

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- Definition

Represents the following effective yield adjustments pertaining to mortgage backed securities. (1) For Agency MBS, this reflects net premium amortization and discount accretion based on actual prepayment activity. (2) For Non-Agency MBS, this is the difference between the net income calculated using the net yield, which is based on management's estimates of future cash flows, less the current coupon yield.

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No definition available.

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- Definition

Amount of operating interest income, including amortization and accretion of premiums and discounts, on securitized, pass-through debt securities collateralized by real estate mortgage loans.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.2)
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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