Residential Loans - Characteristics of Loans Held-for-Investment (Details) - Held-for-investment at fair value $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2023 USD ($) loan	Dec. 31, 2022 USD ($) loan
Legacy Sequoia
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	1,098	1,304
Unpaid principal balance	$ 164,904	$ 204,404
Fair value of loans	$ 150,152	$ 184,932
Weighted average coupon (as a percent)	6.35%	4.51%
Number of loans in foreclosure \| loan	14	11
Unpaid principal balance of loans in foreclosure	$ 2,742	$ 1,166
Sequoia
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	5,460	4,624
Unpaid principal balance	$ 4,624,113	$ 3,847,091
Fair value of loans	$ 3,774,090	$ 3,190,417
Weighted average coupon (as a percent)	3.73%	3.25%
Number of loans in foreclosure \| loan	6	5
Unpaid principal balance of loans in foreclosure	$ 4,842	$ 4,654
Freddie Mac SLST
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	10,448	10,882
Unpaid principal balance	$ 1,641,178	$ 1,719,236
Fair value of loans	$ 1,312,149	$ 1,457,058
Weighted average coupon (as a percent)	4.50%	4.50%
Number of loans in foreclosure \| loan	317	427
Unpaid principal balance of loans in foreclosure	$ 52,918	$ 72,440
Financing Receivables, Equal to Greater than 90 Days Past Due \| Legacy Sequoia
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans with 90+ day delinquencies \| loan	24	30
Fair value of loans with 90+ day delinquencies	$ 5,460	$ 6,824
Financing Receivables, Equal to Greater than 90 Days Past Due \| Sequoia
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans with 90+ day delinquencies \| loan	9	10
Fair value of loans with 90+ day delinquencies	$ 7,599	$ 7,799
Financing Receivables, Equal to Greater than 90 Days Past Due \| Freddie Mac SLST
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans with 90+ day delinquencies \| loan	818	1,211
Fair value of loans with 90+ day delinquencies	$ 139,349	$ 209,397

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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Loans Held-for-Investment, Weighted Average Coupon Rate

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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

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

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-Topic 948
-SubTopic 310
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-Publisher FASB
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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.

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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479851/948-310-S99-1

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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
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

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- Definition

Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(5)(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1

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-Topic 310
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481990/310-10-45-2

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-Topic 326
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This is the sum of principal amount outstanding for both securitized and unsecuritized loans of all types.

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