Principles of Consolidation - Assets and Liabilities of Consolidated Variable Interest Entity's (Detail) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2016 USD ($) Investment	Dec. 31, 2015 USD ($) Investment
Variable Interest Entity [Line Items]
Assets	$ 1,102,195	$ 1,195,574
Liabilities	$ 959,464	$ 1,050,861
Number of VIEs \| Investment	21	22
Sequoia
Variable Interest Entity [Line Items]
Assets	$ 936,096	$ 1,028,124
Liabilities	$ 907,542	$ 997,475
Number of VIEs \| Investment	20	21
Commercial Securitization
Variable Interest Entity [Line Items]
Assets	$ 166,099	$ 167,450
Liabilities	$ 51,922	$ 53,386
Number of VIEs \| Investment	1	1
Residential Loans Held for Investment
Variable Interest Entity [Line Items]
Assets	$ 930,027	$ 1,021,870
Residential Loans Held for Investment \| Sequoia
Variable Interest Entity [Line Items]
Assets	930,027	1,021,870
Residential Loans Held for Investment \| Commercial Securitization
Variable Interest Entity [Line Items]
Assets	0	0
Commercial Loans Held For Investment
Variable Interest Entity [Line Items]
Assets	164,626	166,016
Commercial Loans Held For Investment \| Sequoia
Variable Interest Entity [Line Items]
Assets	0	0
Commercial Loans Held For Investment \| Commercial Securitization
Variable Interest Entity [Line Items]
Assets	164,626	166,016
Real estate securities
Variable Interest Entity [Line Items]
Assets		0
Real estate securities \| Sequoia
Variable Interest Entity [Line Items]
Assets		0
Real estate securities \| Commercial Securitization
Variable Interest Entity [Line Items]
Assets		0
Restricted cash
Variable Interest Entity [Line Items]
Assets	283	365
Restricted cash \| Sequoia
Variable Interest Entity [Line Items]
Assets	147	228
Restricted cash \| Commercial Securitization
Variable Interest Entity [Line Items]
Assets	136	137
Accrued interest receivable
Variable Interest Entity [Line Items]
Assets	2,328	2,428
Accrued interest receivable \| Sequoia
Variable Interest Entity [Line Items]
Assets	1,038	1,131
Accrued interest receivable \| Commercial Securitization
Variable Interest Entity [Line Items]
Assets	1,290	1,297
Other Assets
Variable Interest Entity [Line Items]
Assets	4,931	4,895
Other Assets \| Sequoia
Variable Interest Entity [Line Items]
Assets	4,884	4,895
Other Assets \| Commercial Securitization
Variable Interest Entity [Line Items]
Assets	47	0
Accrued interest payable
Variable Interest Entity [Line Items]
Liabilities	761	804
Accrued interest payable \| Sequoia
Variable Interest Entity [Line Items]
Liabilities	519	555
Accrued interest payable \| Commercial Securitization
Variable Interest Entity [Line Items]
Liabilities	242	249
Accrued expenses and other liabilities
Variable Interest Entity [Line Items]
Liabilities		100
Accrued expenses and other liabilities \| Sequoia
Variable Interest Entity [Line Items]
Liabilities		100
Accrued expenses and other liabilities \| Commercial Securitization
Variable Interest Entity [Line Items]
Liabilities		0
Asset-backed Securities
Variable Interest Entity [Line Items]
Liabilities	958,703	1,049,957
Asset-backed Securities \| Sequoia
Variable Interest Entity [Line Items]
Liabilities	907,023	996,820
Asset-backed Securities \| Commercial Securitization
Variable Interest Entity [Line Items]
Liabilities	$ 51,680	$ 53,137

Number of Variable Interest Entities, Acquired and Consolidated

No definition available.

Name:	rwt_NumberOfVariableInterestEntitiesAcquiredAndConsolidated
Namespace Prefix:	rwt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=52262685&loc=d3e5710-111685

+ Details

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

- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=rwt_CommercialLoansHeldForInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=rwt_RealEstateSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=rwt_RestrictedCashMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=rwt_InterestReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_OtherAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=rwt_InterestPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_AccruedLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: