Long-Term Debt - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended		6 Months Ended
		Nov. 30, 2014	Mar. 31, 2013	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Federal home loan bank stock				$ 30,001,000		$ 30,001,000		$ 10,688,000
Accrued interest payable				2,000,000		2,000,000		2,000,000
Accrued interest payable balance on long-term debt (less than)	[1]			8,291,000		8,291,000		8,503,000
Commercial Secured Borrowings
Debt Instrument [Line Items]
Commercial mortgage loans				$ 65,000,000		$ 65,000,000
Exchangeable Senior Notes
Debt Instrument [Line Items]
Convertible notes		$ 205,000,000
Debt Instrument interest rate		5.625%
Debt instrument maturity year		2019
Debt instrument redemption date		Nov. 15, 2019
Net proceeds from issuance of convertible debt		$ 198,000,000
Interest expense yield				(6.58%)		(6.51%)
Accrued interest payable				$ 2,000,000		$ 2,000,000
Unamortized Debt Issuance Expense				$ 6,000,000		$ 6,000,000
Convertible senior notes conversion rate						0.0461798
Convertible senior notes conversion per share				$ 21.65		$ 21.65
Senior Notes due 2018
Debt Instrument [Line Items]
Convertible notes			$ 288,000,000
Debt Instrument interest rate			4.625%
Net proceeds from issuance of convertible debt			$ 279,000,000
Interest expense yield				(5.41%)		(5.39%)
Accrued interest payable				$ 3,000,000		$ 3,000,000
Unamortized Debt Issuance Expense				$ 5,000,000		$ 5,000,000
Convertible senior notes conversion rate						0.041132
Convertible senior notes conversion per share				$ 24.31		$ 24.31
Trust Preferred Securities
Debt Instrument [Line Items]
Interest expense yield				(2.63%)	(2.67%)	(2.58%)	(2.57%)
Debt instrument face amount				$ 100,000,000		$ 100,000,000
Percentage of yield of debt securities				(6.85%)	(6.89%)	(6.85%)	(6.87%)
Subordinated Notes
Debt Instrument [Line Items]
Interest expense yield				(2.63%)	(2.67%)	(2.58%)	(2.57%)
Debt instrument face amount				$ 40,000,000		$ 40,000,000
Percentage of yield of debt securities				(6.85%)	(6.87%)	(6.85%)	(6.87%)
Long-term Debt | Maximum
Debt Instrument [Line Items]
Accrued interest payable balance on long-term debt (less than)				$ 1,000,000		$ 1,000,000		$ 1,000,000
FHLB Chicago
Debt Instrument [Line Items]
Federal home loan bank advances, reset period of basis margin						91 days
FHLB Chicago | Residential Loans Held For Investment at Fair Value
Debt Instrument [Line Items]
Amount on advances secured by residential mortgage loans				1,000,000,000		$ 1,000,000,000
FHLB Member Subsidiary | FHLB Chicago
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				1,000,000,000		1,000,000,000
Additional borrowings from FHLBC				31,000,000		386,000,000
Federal home loan bank advances outstanding				$ 882,000,000		$ 882,000,000
Weighted average interest rate				0.23%		0.23%
Weighted average maturity						6 years
Federal home loan bank stock				$ 30,000,000		$ 30,000,000

[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 the primary beneficiary (Redwood Trust, Inc.). At June 30, 2015 and December 31, 2014, assets of consolidated VIEs totaled $1,622,636 and $1,900,208, respectively, and liabilities of consolidated VIEs totaled $1,263,249 and $1,546,490, respectively. See Note 4 for further discussion.