Mortgage-Backed Securities - Investment Holdings - Narrative (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Investment Holdings [Line Items]
Gross unrealized loss	$ 217,474	$ 85,984
Agency MBS
Investment Holdings [Line Items]
Gross unrealized loss	115	1,000
Non-Agency RMBS
Investment Holdings [Line Items]
Gross unrealized loss	$ 9,000	$ 348
Non-Agency RMBS Deemed To Be Equivalent To Alt-A Quality
Investment Holdings [Line Items]
Percentage in Alt-A collateral	58.00%	58.00%
Non Agency Residential MBS Deemed To Be Equivalent To Prime Quality
Investment Holdings [Line Items]
Percentage in prime collateral	13.00%	12.00%
Minimum \| Alt-A
Investment Holdings [Line Items]
FICO Score	680
Maximum \| Alt-A
Investment Holdings [Line Items]
FICO Score	720
Alt-A securities underlying collateral of full documented loans	30.00%
Non-Agency RMBS
Investment Holdings [Line Items]
Market value of investments transferred	$ 135,000

Financing Receivable, Credit Quality, Alt-A Securities Underlying Collateral, FICO Score

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- Definition

Financing Receivable, Credit Quality, Alt A Securities Underlying Collateral of Full Documented Loans, Percent

+ References

No definition available.

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- Definition

As of the balance sheet date, the percentage of the mortgages securing the RMBS that meet defined criteria to be categorized as Alt-A.

+ References

No definition available.

+ Details

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- Definition

As of the balance sheet date, the percentage of the mortgages securing the RMBS that meet defined criteria to be categorized as prime.

+ References

No definition available.

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- Definition

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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Section 50
-Paragraph 2
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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.

+ References

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- Definition

Amount conveyed to unrelated parties of contract to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122739-111746

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