Residential Loans - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
Mar. 31, 2015 Contract	Mar. 31, 2014	Dec. 31, 2014 Contract
Mortgage Loans on Real Estate [Line Items]
Principal balance of loans sold during period	$ 2,200,000,000	$ 707,000,000
Carrying value	3,399,755,000		3,398,573,000
Sequoia
Mortgage Loans on Real Estate [Line Items]
Carrying value	1,304,426,000		1,474,386,000
Fixed-rate loans
Mortgage Loans on Real Estate [Line Items]
Weighted average coupon rate	3.92%
Hybrid loans
Mortgage Loans on Real Estate [Line Items]
Weighted average coupon rate	3.06%
Residential Loans at Fair Value
Mortgage Loans on Real Estate [Line Items]
Number of loans	1,903		2,273
Loan Principal	1,070,000,000		1,300,000,000
Principal value of loans purchased	2,400,000,000	1,070,000,000
Valuation adjustments	2,056,000	7,128,000
Residential Loans at Lower of Cost or Fair Value
Mortgage Loans on Real Estate [Line Items]
Number of loans	9		9,000
Loan Principal	2,000,000		0
Carrying value	1,472,000		1,488,000
Residential Loans at Lower of Cost or Fair Value \| Sequoia
Mortgage Loans on Real Estate [Line Items]
Carrying value	0		0
Residential Loans Held For Investment at Fair Value
Mortgage Loans on Real Estate [Line Items]
Number of loans	1,314		803
Loan Principal	972,000,000		566,000,000
Carrying value	1,000,000,000
Principal balance of loans transferred	436,000,000
Fair value of loans transferred	448,000,000
Loan pledged as collateral	994,000,000
Weighted average original Fair Isaac Corporation (FICO) score	773
Weighted average original loan-to-value (LTV)	68.00%
Residential Loans Held For Investment at Fair Value \| Sequoia
Mortgage Loans on Real Estate [Line Items]
Number of loans	5,177		5,315
Weighted average original Fair Isaac Corporation (FICO) score	733
Weighted average original loan-to-value (LTV)	66.00%
Loans held-for-investment, delinquent greater than 90 days	68,000,000		73,000,000
Loans held-for-investment, in foreclosure	34,000,000		39,000,000
Valuation adjustments	3,000,000
Residential Loans Held for Investment
Mortgage Loans on Real Estate [Line Items]
Loan Principal	1,415,017,000		1,483,213,000
Carrying value	1,304,426,000		1,474,386,000
Unamortized premium, net	0		12,511,000
Allowance for loan losses	0		21,338,000
Mortgage Servicing Rights
Mortgage Loans on Real Estate [Line Items]
Purchases of mortgage servicing assets	$ 1,908,993,000

Fair Value Of Loans Securitized During Period

No definition available.

Name:	rwt_FairValueOfLoansSecuritizedDuringPeriod
Namespace Prefix:	rwt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair Value, Option, Loans Held As Assets, Aggregate Amount In Foreclosure

+ References

No definition available.

+ Details

Name:	rwt_FairValueOptionLoansHeldAsAssetsAggregateAmountInForeclosure
Namespace Prefix:	rwt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The weighted average FICO score for borrowers at the time loans were originated.

+ References

No definition available.

+ Details

Name:	rwt_FinancingReceivableCreditScoreFICOWeightedAverage
Namespace Prefix:	rwt_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Financing Receivable, Loan To Value Ratio

+ References

No definition available.

+ Details

Name:	rwt_FinancingReceivableLoanToValueRatio
Namespace Prefix:	rwt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Financing Receivables, Weighted Average Interest Rate

+ References

No definition available.

+ Details

Name:	rwt_FinancingReceivablesWeightedAverageInterestRate
Namespace Prefix:	rwt_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Principal Amount Of Loans Securitized During Period

+ References

No definition available.

+ Details

Name:	rwt_PrincipalAmountOfLoansSecuritizedDuringPeriod
Namespace Prefix:	rwt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Principal Balance of Loans Acquired During Period

+ References

No definition available.

+ Details

Name:	rwt_PrincipalBalanceOfLoansAcquiredDuringPeriod
Namespace Prefix:	rwt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Principal Balance of Loans Sold During Period

+ References

No definition available.

+ Details

Name:	rwt_PrincipalBalanceofLoansSoldDuringPeriod
Namespace Prefix:	rwt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 310

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6873192&loc=d3e21338-158488

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 30

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

+ Details

Name:	us-gaap_FairValueOptionChangesInFairValueGainLoss1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the aggregate fair value of loans held as assets that are 90 days or more past due for which the fair value option has been elected.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 28

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

+ Details

Name:	us-gaap_FairValueOptionLoansHeldAsAssets90DaysOrMorePastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of consumer loans, including, but not limited to, mortgage, home equity, vehicles, credit card, installment, and lease financing. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5074-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5066-111524

+ Details

Name:	us-gaap_LoansAndLeasesReceivableNetReportedAmountConsumer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5086-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6467456&loc=d3e113888-111728

+ Details

Name:	us-gaap_LoansPledgedAsCollateral
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Definition

Indicates the number of mortgages under each classification.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule IV)

-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29.3)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule IV

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 29

-Paragraph 3

-Article 12

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateNumberOfLoans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The total periodic movement (increases and decreases) in the carrying amount of mortgage loans on real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule IV)

-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 29

-Article 12

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule IV

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29.6)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

+ Details

Name:	us-gaap_MortgageLoansOnRealEstatePeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

This is the sum of principal amount outstanding for both securitized and unsecuritized loans of all types.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719

+ Details

Name:	us-gaap_PrincipalAmountOutstandingOnLoansManagedAndSecuritized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of additions from purchases, assumption or transfer to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 50

-Section 50

-Paragraph 4

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=7882072&loc=d3e122739-111746

+ Details

Name:	us-gaap_ServicingAssetAtAmortizedValueAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6378536&loc=d3e10092-111533

+ Details

Name:	us-gaap_UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rwt_ResidentialLoansAtFairValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rwt_ResidentialLoansAtLowerOfCostOrFairValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rwt_ResidentialLoansHeldForInvestmentAtFairValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=rwt_ResidentialLoansHeldForInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=rwt_MortgageServicingRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=rwt_SequoiaSecuritizationEntitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: