Residential Loans - Characteristics of Loans Held-for-Investment (Details) - Held-for-investment at fair value $ in Thousands	Sep. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Legacy Sequoia
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	1,976	2,198
Unpaid principal balance	$ 352,392	$ 424,829
Loans, at fair value	$ 296,765	$ 407,890
Number of loans in foreclosure \| loan	21	16
Fair value of loans, in foreclosure	$ 4,820	$ 3,673
Legacy Sequoia \| Financing Receivables, Equal to Greater than 90 Days Past Due
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans past due \| loan	49	39
Fair value of loans with 90+ day delinquencies	$ 16,076	$ 9,803
Sequoia Choice
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	2,546	3,156
Unpaid principal balance	$ 1,811,967	$ 2,240,679
Loans, at fair value	$ 1,836,361	$ 2,291,463
Number of loans in foreclosure \| loan	3	3
Fair value of loans, in foreclosure	$ 1,814	$ 2,290
Sequoia Choice \| Financing Receivables, Equal to Greater than 90 Days Past Due
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans past due \| loan	132	9
Fair value of loans with 90+ day delinquencies	$ 102,693	$ 6,755
Freddie Mac SLST
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	13,893	14,502
Unpaid principal balance	$ 2,304,047	$ 2,428,035
Loans, at fair value	$ 2,256,683	$ 2,367,215
Number of loans in foreclosure \| loan	175	208
Fair value of loans, in foreclosure	$ 28,380	$ 33,042
Freddie Mac SLST \| Financing Receivables, Equal to Greater than 90 Days Past Due
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans past due \| loan	1,772	587
Fair value of loans with 90+ day delinquencies	$ 339,537	$ 134,680
Redwood
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	0	2,940
Unpaid principal balance	$ 0	$ 2,052,778
Loans, at fair value	$ 0	$ 2,111,897
Number of loans in foreclosure \| loan	0	0
Fair value of loans, in foreclosure	$ 0	$ 0
Redwood \| Financing Receivables, Equal to Greater than 90 Days Past Due
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Unpaid principal balance	$ 0	$ 1,424
Number of loans past due \| loan	0	2
Fair value of loans with 90+ day delinquencies	$ 0	$ 1,585

Fair Value, Option, Loans Held As Assets, Aggregate Amount In Foreclosure

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Financing Receivable, Number Of Loans In Foreclosure

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Financing Receivable, Number Of Loans Past Due

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No definition available.

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- Definition

Number of mortgage loans within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Footnote 3
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Footnote 3))
-URI http://asc.fasb.org/extlink&oid=120402547&loc=d3e617274-123014

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This item represents the aggregate fair value of loans held as assets that are 90 days or more past due for which the fair value option has been elected.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (e)(1)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612

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- Definition

Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919230-210447

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522

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- Definition

This is the sum of principal amount outstanding for both securitized and unsecuritized loans of all types.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719

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