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Long-Term Debt - Additional Information (Details) - USD ($) | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Aug. 31, 2017 | Jan. 31, 2016 | Nov. 30, 2014 | Mar. 31, 2013 | Sep. 30, 2017 | Jun. 30, 2017 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Transition period for subsidiary to be a FHLB-member (in years) |  |  | 5 years |  |  |  |  |  |  |
Existing debt |  |  |  |  |  | $ 0 |  | $ 0 |  | $ 0
Federal home loan bank stock |  |  |  |  |  | 43,393,000 |  | 43,393,000 |  | 43,393,000
Accrued interest payable |  |  |  |  |  | 5,000,000 |  | 5,000,000 |  | 3,000,000
Notional amount |  |  |  |  |  | 6,244,759,000 |  | 6,244,759,000 |  | 4,980,343,000
Accrued interest payable | [1] |  |  |  |  | $ 18,836,000 |  | $ 18,836,000 |  | 9,608,000
Trust Preferred Securities And Subordinated Notes |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Weighted average interest rates, by series |  |  |  |  |  | 6.80% |  | 6.80% |  |
Accrued interest payable |  |  |  |  |  | $ 1,000,000 |  | $ 1,000,000 |  | 1,000,000
Trust Preferred Securities And Subordinated Notes | Interest rate swaps |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  |  |  | 140,000,000 |  | $ 140,000,000 |  |
Trust Preferred Securities And Subordinated Notes | LIBOR |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Basis spread on variable rate |  |  |  |  |  |  |  | 2.25% |  |
Trust Preferred Securities |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Debt instrument face amount |  |  |  |  |  | 100,000,000 |  | $ 100,000,000 |  |
Subordinated Notes |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Debt instrument face amount |  |  |  |  |  | 40,000,000 |  | 40,000,000 |  |
Senior Notes Due 2023 | Convertible Debt |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Convertible notes |  | $ 245,000,000 |  |  |  | $ 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 senior notes conversion rate |  |  |  |  |  |  |  | 0.0538394 |  |
Convertible senior notes conversion per share (in dollars per share) |  |  |  |  |  | $ 18.57 |  | $ 18.57 |  |
Accrued interest payable |  |  |  |  |  | $ 1,000,000 |  | $ 1,000,000 |  |
Unamortized debt issuance costs |  |  |  |  |  | 7,000,000 |  | 7,000,000 |  |
Exchangeable Senior Notes Due 2019 | Convertible Debt |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Convertible notes |  |  |  | $ 205,000,000 |  | $ 201,000,000 |  | $ 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 senior notes conversion rate |  |  |  |  |  |  |  | 0.0461798 |  |
Convertible senior notes conversion per share (in dollars per share) |  |  |  |  |  | $ 21.65 |  | $ 21.65 |  |
Accrued interest payable |  |  |  |  |  | $ 4,000,000 |  | $ 4,000,000 |  |
Unamortized debt issuance costs |  |  |  |  |  | 3,000,000 |  | 3,000,000 |  |
Debt instrument redemption date |  |  |  | Nov. 15, 2019 |  |  |  |  |  |
Amount of debt repurchased |  |  |  |  |  | $ 0 |  | $ 0 | $ 4,000,000 |
Exchangeable Senior Notes Due 2019 | Convertible Debt | Gain (loss) on investments |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Gain on extinguishment of debt |  |  |  |  |  |  |  |  | $ 300,000 |
Convertible Senior Notes Due 2018 | Convertible Debt |  |  |  |  |  |  |  |  |  |
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 senior notes conversion rate |  |  |  |  |  |  |  | 0.0411320 |  |
Convertible senior notes conversion per share (in dollars per share) |  |  |  |  |  | $ 24.31 |  | $ 24.31 |  |
Accrued interest payable |  |  |  |  |  | $ 5,000,000 |  | $ 5,000,000 |  |
Unamortized debt issuance costs |  |  |  |  |  | 300,000 |  | 300,000 |  |
Amount of debt repurchased |  |  |  |  |  |  | 37,000,000 |  |  |
Gain on extinguishment of debt |  |  |  |  |  |  | (1,000,000) |  |  |
Unamortized deferred issuance costs |  |  |  |  |  |  | $ 2,000,000 |  |  |
Current maturities of long-term debt |  |  |  |  |  | 250,000,000 |  | $ 250,000,000 |  |
FHLB Chicago |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Federal home loan bank advances, reset period of basis margin (in days) |  |  |  |  |  |  |  | 91 days |  |
FHLB Chicago | Held-for-sale residential loans |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Loans pledged as collateral under borrowing agreement with FHLBC |  |  |  |  |  | 2,260,000,000 |  | $ 2,260,000,000 |  |
FHLB Chicago | Cash [Member] |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Loans pledged as collateral under borrowing agreement with FHLBC |  |  |  |  |  | 24,000,000 |  | 24,000,000 |  |
FHLB Member Subsidiary | FHLB Chicago |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |
Maximum borrowing limit |  |  |  |  |  | 2,000,000,000 |  | 2,000,000,000 |  |
Additional borrowings from FHLBC |  |  |  |  |  | 0 |  | 0 |  |
Existing debt |  |  |  |  |  | 2,000,000,000 |  | 2,000,000,000 |  |
Federal home loan bank advances outstanding |  |  |  |  |  | $ 2,000,000,000 |  | $ 2,000,000,000 |  | $ 2,000,000,000
Weighted average interest rate |  |  |  |  |  | 1.30% |  | 1.30% |  | 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 September 30, 2017 and December 31, 2016, assets of consolidated VIEs totaled $995,768 and $798,317, respectively. At September 30, 2017 and December 31, 2016, liabilities of consolidated VIEs totaled $945,873 and $773,980, respectively. See Note 4 for further discussion.

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- 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 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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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + 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 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + 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 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Weighted average interest rate of long-term debt outstanding. + References No definition available. + Details
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- Definition The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination. + References No definition available. + Details
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- Definition Amount of cash inflow from proceeds of Federal Home Loan Bank (FHLBank) advances. + References No definition available. + Details
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- Definition The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset. + 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 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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