Principles of Consolidation - Assumptions Related to Assets Retained from Unconsolidated VIEs Sponsored by Redwood (Details) - Variable Interest Entity, Not Primary Beneficiary	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
MSRs
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities [Line Items]
Prepayment rates	9.00%	21.00%
Discount rates	11.00%	11.00%
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	10.00%
Discount rates	14.00%
Credit loss assumptions	0.25%
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	10.00%	15.00%
Discount rates	5.00%	6.00%
Credit loss assumptions	0.25%	0.25%

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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=64830801&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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107207-111719

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- Definition

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+ 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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64830801&loc=d3e107207-111719

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