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Fair Value of Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2015
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Dealer marks of securities | 81.00%rwt_PercentageOfDealerQuotesReceivedOnSecurities
Percentage of carrying value for which dealer quotes have been received | 93.00%rwt_PercentageOfCarryingValueForWhichDealerQuotesWereReceivedOnSecurities
Percentage difference of internal valuation than dealer marks | 2.00%rwt_PercentageDifferenceOfInternalValuationThanDealerMarks
Residential Subordinate Securities |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Fair value option elected aggregate carrying amount, asset | $ 23 rwt_FairValueOptionAssetsAggregateCarryingAmountDuringPeriod / invest_InvestmentSecuritiesClassAxis = rwt_ResidentialSubordinateSecuritiesMember
Residential Loans |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Fair value option elected aggregate carrying amount, asset | 2,400 rwt_FairValueOptionAssetsAggregateCarryingAmountDuringPeriod / invest_InvestmentSecuritiesClassAxis = rwt_ResidentialLoansMember
Commercial Loans |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Fair value option elected aggregate carrying amount, asset | 93 rwt_FairValueOptionAssetsAggregateCarryingAmountDuringPeriod / invest_InvestmentSecuritiesClassAxis = us-gaap_CommercialLoanMember
Mortgage Servicing Rights |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Fair value option elected aggregate carrying amount, asset | $ 19 rwt_FairValueOptionAssetsAggregateCarryingAmountDuringPeriod / invest_InvestmentSecuritiesClassAxis = rwt_MortgageServicingRightsMember
Mortgage Servicing Rights | Maximum |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Percentage difference of internal valuation than dealer marks | 2.00%rwt_PercentageDifferenceOfInternalValuationThanDealerMarks / us-gaap_InvestmentTypeAxis = rwt_MortgageServicingRightsMember / us-gaap_RangeAxis = us-gaap_MaximumMember
Asset-backed Securities |
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items] |
Dealer marks of securities | 36.00%rwt_PercentageOfDealerQuotesReceivedOnSecurities / us-gaap_InvestmentTypeAxis = us-gaap_AssetBackedSecuritiesMember
Percentage difference of internal valuation than dealer marks | 1.00%rwt_PercentageDifferenceOfInternalValuationThanDealerMarks / us-gaap_InvestmentTypeAxis = us-gaap_AssetBackedSecuritiesMember

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- Definition Fair Value, Option, Assets, Aggregate Carrying Amount During Period + References No definition available. + Details
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- Definition Percentage Difference Of Internal Valuation Than Dealer Marks + References No definition available. + Details
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- Definition Percentage of Carrying Value for Which Dealer Quotes Were Received on Securities + References No definition available. + Details
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- Definition Percentage of Third-party Dealer Quotes Received on Securities. + References No definition available. + Details
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