Summary of Significant Accounting Policies - Offsetting of Financial Assets, Liabilities, and Collateral (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Offsetting Asset and Liabilities [Line Items]
Derivative assets	[1]	$ 15,718	$ 36,595
Gross Amounts of Recognized Liabilities		(1,747,787)	(854,067)
Gross Amounts Offset in Consolidated Balance Sheet		0	0
Net Amounts of Liabilities Presented in Consolidated Balance Sheet - Derivatives	[1]	(63,081)	(66,329)
Net Amounts of Liabilities Presented in Consolidated Balance Sheet		(1,747,787)	(854,067)
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments		1,694,741	803,211
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Pledged		50,747	50,111
Net Amount		(2,299)	(745)
Interest Rate Agreement, TBAs, And Futures
Offsetting Asset and Liabilities [Line Items]
Gross Amounts of Recognized Assets		10,298	33,280
Gross Amounts Offset in Consolidated Balance Sheet		0	0
Derivative assets		10,298	33,280
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments		(6,329)	(11,672)
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Received		(42)	(9,148)
Net Amount		3,927	12,460
Interest rate agreements
Offsetting Asset and Liabilities [Line Items]
Gross Amounts of Recognized Assets		10,164	24,980
Gross Amounts Offset in Consolidated Balance Sheet		0	0
Derivative assets		10,164	24,980
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments		(6,196)	(7,736)
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Received		(42)	(4,784)
Net Amount		3,926	12,460
Gross Amounts of Recognized Liabilities - Derivatives		(55,567)	(56,919)
Gross Amounts Offset in Consolidated Balance Sheet - Derivatives		0	0
Net Amounts of Liabilities Presented in Consolidated Balance Sheet - Derivatives		(55,567)	(56,919)
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments - Derivatives		6,196	7,736
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Pledged - Derivatives		49,371	49,183
Net Amount - Derivatives		0	0
TBAs
Offsetting Asset and Liabilities [Line Items]
Gross Amounts of Recognized Assets		133	8,300
Gross Amounts Offset in Consolidated Balance Sheet		0	0
Derivative assets		133	8,300
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments		(133)	(3,936)
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Received		0	(4,364)
Net Amount		0	0
Gross Amounts of Recognized Liabilities - Derivatives		(3,808)	(4,681)
Gross Amounts Offset in Consolidated Balance Sheet - Derivatives		0	0
Net Amounts of Liabilities Presented in Consolidated Balance Sheet - Derivatives		(3,808)	(4,681)
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments - Derivatives		133	3,936
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Pledged - Derivatives		1,376	0
Net Amount - Derivatives		(2,299)	(745)
Futures
Offsetting Asset and Liabilities [Line Items]
Gross Amounts of Recognized Assets		1
Gross Amounts Offset in Consolidated Balance Sheet		0
Derivative assets		1
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments		0
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Received		0
Net Amount		1
Gross Amounts of Recognized Liabilities - Derivatives			(928)
Gross Amounts Offset in Consolidated Balance Sheet - Derivatives			0
Net Amounts of Liabilities Presented in Consolidated Balance Sheet - Derivatives			(928)
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments - Derivatives			0
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Pledged - Derivatives			928
Net Amount - Derivatives			0
Loan warehouse debt
Offsetting Asset and Liabilities [Line Items]
Gross Amounts of Recognized Liabilities - Other		(1,039,666)	(485,544)
Gross Amounts Offset in Consolidated Balance Sheet - Other		0	0
Net Amounts of Liabilities Presented in Consolidated Balance Sheet - Other		(1,039,666)	(485,544)
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments - Other		1,039,666	485,544
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Pledged - Other		0	0
Net Amount - Other		0	0
Security repurchase agreements
Offsetting Asset and Liabilities [Line Items]
Gross Amounts of Recognized Liabilities - Other		(648,746)	(305,995)
Gross Amounts Offset in Consolidated Balance Sheet - Other		0	0
Net Amounts of Liabilities Presented in Consolidated Balance Sheet - Other		(648,746)	(305,995)
Gross Amounts Not Offset in Consolidated Balance Sheet, Financial Instruments - Other		648,746	305,995
Gross Amounts Not Offset in Consolidated Balance Sheet, Cash Collateral Pledged - Other		0	0
Net Amount - Other		$ 0	$ 0

[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 December 31, 2017 and December 31, 2016, assets of consolidated VIEs totaled $1,259,774 and $798,317, respectively. At December 31, 2017 and December 31, 2016, liabilities of consolidated VIEs totaled $1,167,157 and $773,980, respectively. See Note 4 for further discussion.