Segment Information - Components of Corporate/Other (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Interest income		$ 71,468	$ 62,737	$ 59,224	$ 54,628	$ 56,334	$ 60,906	$ 66,787	$ 62,328	$ 248,057	$ 246,355	$ 259,432
Interest expense		(36,108)	(27,443)	(24,234)	(21,031)	(20,537)	(21,597)	(22,444)	(23,950)	(108,816)	(88,528)	(95,883)
Net Interest Income		35,360	35,294	34,990	33,597	35,797	39,309	44,343	38,378	139,241	157,827	163,549
Mortgage banking activities, net										53,908	38,691	10,972
Investment fair value changes, net										10,374	(28,574)	(21,357)
Realized gains, net										13,355	28,009	36,369
Total non-interest income, net		10,951	26,070	25,297	27,755	9,763	33,712	10,888	4,454	90,073	58,817	25,254
Direct operating expenses		(20,367)	(19,922)	(18,641)	(18,226)	(17,824)	(20,355)	(20,155)	(30,452)	(77,156)	(88,786)	(97,416)
Benefit from income taxes										(11,752)	(3,708)	10,346
Net Income		30,933	$ 36,180	$ 36,324	$ 36,969	25,355	$ 52,553	$ 41,281	$ 12,063	140,406	131,252	102,088
Real estate securities	[1]	1,476,510				1,018,439				1,476,510	1,018,439
Mortgage servicing rights	[1]	63,598				118,526				63,598	118,526
Total assets	[1]	7,039,822				5,483,477				7,039,822	5,483,477
Residential Loans
Segment Reporting Information [Line Items]
Residential loans		5,115,210				3,888,051				5,115,210	3,888,051
Operating Segments | Investment Portfolio
Segment Reporting Information [Line Items]
Interest income										188,760	192,200	177,595
Interest expense										(36,690)	(22,997)	(22,684)
Net Interest Income										152,070	169,203	154,911
Mortgage banking activities, net										0	0	0
Investment fair value changes, net										18,414	(24,367)	(20,089)
Realized gains, net										14,107	27,717	36,369
Total non-interest income, net										44,957	24,041	15,550
Direct operating expenses										(6,028)	(10,421)	(7,179)
Benefit from income taxes										(5,328)	(1,848)	846
Net Income										185,671	188,077	164,483
Real estate securities		1,476,510				1,018,439				1,476,510	1,018,439
Mortgage servicing rights		63,598				118,526				63,598	118,526
Total assets		4,743,873				3,615,535				4,743,873	3,615,535
Operating Segments | Investment Portfolio | Residential Loans
Segment Reporting Information [Line Items]
Residential loans		3,054,448				2,261,016				3,054,448	2,261,016
Operating Segments | Residential Mortgage Banking
Segment Reporting Information [Line Items]
Interest income										39,309	33,661	52,260
Interest expense										(17,369)	(14,191)	(17,207)
Net Interest Income										21,940	19,470	35,053
Mortgage banking activities, net										53,908	40,753	8,268
Investment fair value changes, net										0	0	0
Realized gains, net										0	0	0
Total non-interest income, net										53,908	40,753	8,268
Direct operating expenses										(25,113)	(23,252)	(43,182)
Benefit from income taxes										(6,424)	(1,860)	4,169
Net Income										44,311	35,111	4,308
Real estate securities		0				0				0	0
Mortgage servicing rights		0				0				0	0
Total assets		1,453,069				866,356				1,453,069	866,356
Operating Segments | Residential Mortgage Banking | Residential Loans
Segment Reporting Information [Line Items]
Residential loans		1,427,945				835,399				1,427,945	835,399
Corporate/ Other
Segment Reporting Information [Line Items]
Interest income										19,988	20,494	29,577
Interest expense										(54,757)	(51,340)	(55,992)
Net Interest Income										(34,769)	(30,846)	(26,415)
Mortgage banking activities, net										0	(2,062)	2,704
Investment fair value changes, net										(8,040)	(4,207)	(1,268)
Realized gains, net										(752)	292	0
Total non-interest income, net										(8,792)	(5,977)	1,436
Direct operating expenses										(46,015)	(55,113)	(47,055)
Benefit from income taxes										0	0	5,331
Net Income										(89,576)	(91,936)	(66,703)
Real estate securities		0				0				0	0
Mortgage servicing rights		0				0				0	0
Total assets		842,880				1,001,586				842,880	1,001,586
Corporate/ Other | Residential Loans
Segment Reporting Information [Line Items]
Residential loans		$ 632,817				$ 791,636				632,817	791,636
Corporate/ Other | Legacy Consolidated VIEs
Segment Reporting Information [Line Items]
Interest income										19,407	19,537	24,814
Interest expense										(14,789)	(13,103)	(15,646)
Net Interest Income										4,618	6,434	9,168
Mortgage banking activities, net										0	0	0
Investment fair value changes, net										(8,027)	(4,200)	(1,192)
Realized gains, net										0	0	0
Total non-interest income, net										(8,027)	(4,200)	(1,192)
Direct operating expenses										0	0	0
Benefit from income taxes										0	0	0
Net Income										(3,409)	2,234	7,976
Corporate/ Other | Other
Segment Reporting Information [Line Items]
Interest income										581	957	4,763
Interest expense										(39,968)	(38,237)	(40,346)
Net Interest Income										(39,387)	(37,280)	(35,583)
Mortgage banking activities, net										0	(2,062)	2,704
Investment fair value changes, net										(13)	(7)	(76)
Realized gains, net										(752)	292	0
Total non-interest income, net										(765)	(1,777)	2,628
Direct operating expenses										(46,015)	(55,113)	(47,055)
Benefit from income taxes										0	0	5,331
Net Income										$ (86,167)	$ (94,170)	$ (74,679)

[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.