Principles of Consolidation - Assumptions Related to Unconsolidated Variable Interest Entity's Sponsored by Redwood (Details) - Variable Interest Entity, Not Primary Beneficiary	3 Months Ended
Mar. 31, 2021
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	12.00%
Discount rates	15.00%
Credit loss assumptions	0.22%
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	12.00%
Discount rates	6.00%
Credit loss assumptions	0.22%

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

+ Details

Name:	us-gaap_AssumptionForFairValueOnSecuritizationDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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

+ Details

Name:	us-gaap_AssumptionForFairValueOnSecuritizationDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesExpectedCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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.

+ Details

Name:	us-gaap_AssumptionForFairValueOnSecuritizationDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

+ Details

Name:	us-gaap_AssumptionForFairValueOnSecuritizationDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesPrepaymentSpeed
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancialInstrumentAxis=rwt_SeniorSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=rwt_SubordinateSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: