Principles of Consolidation - Assumptions Related to Unconsolidated Variable Interest Entity's Sponsored by Redwood (Details) - Variable Interest Entity, Not Primary Beneficiary	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Senior IO Securities
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment rates	37.00%	41.00%	25.00%
Discount rates	14.00%	16.00%	14.00%
Credit loss assumptions	0.20%	0.21%	0.20%
Subordinate Securities
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment rates	15.00%	13.00%	15.00%
Discount rates	7.00%	6.00%	7.00%
Credit loss assumptions	0.20%	0.22%	0.20%

Discount rate which is used to value residual cash flows generated by financial assets of the securitization, asset-backed financing arrangement, or similar transfer for initial fair value measurement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719

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- Definition

Rate at which principal will not be repaid on securitized financial assets, including for example, but not limited to, expected static pool losses for initial fair value measurement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719

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- Definition

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

No definition available.

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- Definition

Estimated rate of prepayment of principal on financial assets for initial fair value measurement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719

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