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Long-Term Debt - Additional Information (Details) - USD ($) | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Aug. 31, 2017 | Jan. 31, 2016 | Nov. 30, 2014 | Mar. 31, 2013 | Jun. 30, 2017 | Dec. 31, 2017 | Dec. 31, 2016
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Committed line of credit with financial institutions, outstanding |  |  |  |  |  |  | $ 0 | $ 0
FHLB transition period |  |  | 5 years |  |  |  |  |
Federal home loan bank stock |  |  |  |  |  |  | 43,393,000 | 43,393,000
Accrued interest payable |  |  |  |  |  |  | 2,000,000 | 1,000,000
Notional Amount |  |  |  |  |  |  | 6,644,081,000 | 4,980,343,000
Accrued interest payable (less than) | [1] |  |  |  |  |  | 18,435,000 | 9,608,000
Convertible notes | Senior Notes Due 2023 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Convertible notes |  | $ 245,000,000 |  |  |  |  | $ 245,000,000 |
Debt instrument interest rate |  | 4.75% |  |  |  |  |  |
Debt instrument, maturity year |  | 2023 |  |  |  |  |  |
Net proceeds from issuance of convertible debt |  | $ 238,000,000 |  |  |  |  |  |
Interest expense yield |  |  |  |  |  |  | 5.30% |
Convertible debt, conversion ratio |  |  |  |  |  |  | 0.0538394 |
Convertible senior notes conversion per share (in dollars per share) |  |  |  |  |  |  | $ 18.57 |
Accrued interest payable |  |  |  |  |  |  | $ 4,000,000 |
Unamortized deferred issuance costs |  |  |  |  |  |  | (7,000,000) |
Convertible notes | Exchangeable senior notes due 2019 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Convertible notes |  |  |  | $ 205,000,000 |  |  | $ 201,000,000 |
Debt instrument interest rate |  |  |  | 5.625% |  |  |  |
Debt instrument, maturity year |  |  |  | 2019 |  |  |  |
Net proceeds from issuance of convertible debt |  |  |  | $ 198,000,000 |  |  |  |
Interest expense yield |  |  |  |  |  |  | 6.30% |
Convertible debt, conversion ratio |  |  |  |  |  |  | 0.0461798 |
Convertible senior notes conversion per share (in dollars per share) |  |  |  |  |  |  | $ 21.65 |
Accrued interest payable |  |  |  |  |  |  | $ 1,000,000 |
Unamortized deferred issuance costs |  |  |  |  |  |  | (2,000,000) |
Debt instrument, redemption date |  |  |  | Nov. 15, 2019 |  |  |  |
Repurchased debt instrument, face amount |  |  |  |  |  |  | $ 0 | 4,000,000
Convertible notes | Exchangeable senior notes due 2019 | Gain (Loss) on Investments |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Gain (loss) on extinguishment of debt |  |  |  |  |  |  |  | 300,000
Convertible notes | Convertible senior notes due 2018 |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Convertible notes |  |  |  |  | $ 288,000,000 | $ 288,000,000 |  |
Debt instrument interest rate |  |  |  |  | 4.625% |  |  |
Net proceeds from issuance of convertible debt |  |  |  |  | $ 279,000,000 |  |  |
Interest expense yield |  |  |  |  |  |  | 4.80% |
Convertible debt, conversion ratio |  |  |  |  |  |  | 0.041132 |
Convertible senior notes conversion per share (in dollars per share) |  |  |  |  |  |  | $ 24.31 |
Accrued interest payable |  |  |  |  |  |  | $ 2,000,000 |
Unamortized deferred issuance costs |  |  |  |  |  |  | (200,000) |
Repurchased debt instrument, face amount |  |  |  |  |  | 37,000,000 |  |
Gain (loss) on extinguishment of debt |  |  |  |  |  | (1,000,000) |  |
Deferred debt issuance costs |  |  |  |  |  | $ 2,000,000 |  |
Current maturities of long-term debt |  |  |  |  |  |  | 250,000,000 |
Trust Preferred Securities |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument face amount |  |  |  |  |  |  | $ 100,000,000 |
Interest expense yield on trust preferred securities and subordinated notes |  |  |  |  |  |  | (6.90%) |
Subordinated Notes |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Debt instrument face amount |  |  |  |  |  |  | $ 40,000,000 |
Trust Preferred Securities and Subordinated Notes |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Accrued interest payable (less than) |  |  |  |  |  |  | 1,000,000 | 1,000,000
Trust Preferred Securities and Subordinated Notes | Interest rate agreements |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Notional Amount |  |  |  |  |  |  | $ 140,000,000 |
Trust Preferred Securities and Subordinated Notes | London Interbank Offered Rate (LIBOR) |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Basis spread on variable rate |  |  |  |  |  |  | 2.25% |
FHLB Chicago | Redwood | Held-for sale residential loans |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Residential mortgage loans securing FHLB advances |  |  |  |  |  |  | $ 2,430,000,000 |
Subsidiaries | FHLB Chicago |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  | 2,000,000,000 |
Additional borrowings from FHLB |  |  |  |  |  |  |  | 519,000,000
Committed line of credit with financial institutions, outstanding |  |  |  |  |  |  | 2,000,000,000 |
Outstanding FHLB advances |  |  |  |  |  |  | $ 2,000,000,000 | $ 2,000,000,000
Weighted average interest rate |  |  |  |  |  |  | 1.38% | 0.64%
Weighted average maturity (in years) |  |  |  |  |  |  | 8 years | 9 years
[1] | Our consolidated balance sheets include assets of consolidated variable interest entities (“VIEs”) that can only be used to settle obligations of these VIEs and liabilities of consolidated VIEs for which creditors do not have recourse to Redwood Trust, Inc. or its affiliates. At December 31, 2017 and December 31, 2016, assets of consolidated VIEs totaled $1,259,774 and $798,317, respectively. At December 31, 2017 and December 31, 2016, liabilities of consolidated VIEs totaled $1,167,157 and $773,980, respectively. See Note 4 for further discussion.

X
- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Including the current and noncurrent portions, carrying value as of the balance sheet date of a written promise to pay a note, initially due after one year or beyond the operating cycle if longer, which can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(13)) -URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)(a)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of the collateral pledged in support of federal home loan bank advances outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823 + Details
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- Definition Amount of interest payable on debt, including, but not limited to, trade payables. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.15(5)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.15(a)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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