Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Assets
Trading securities		$ 1,013,785	$ 1,118,612
Available-for-sale securities		271,641	333,882
MSRs		204,946	286,778
Derivative assets	[1]	43,649	35,789
Pledged collateral		57,832	42,433
Liabilities
Contingent consideration		25,167	0
Derivative liabilities	[1]	234,011	84,855
Fair Value, Measurements, Recurring
Assets
Business purpose residential loans		336,035	141,258
Multifamily loans		3,791,622	2,144,598
Trading securities		1,013,785	1,118,612
Available-for-sale securities		271,641	333,882
Servicer advance investments		222,591	300,468
MSRs		39,837	60,281
Excess MSRs		32,937	27,312
Shared home appreciation options		11,372
Derivative assets		43,649	35,789
Pledged collateral		57,832	42,433
FHLBC stock		43,393	43,393
Guarantee asset		1,784	2,618
Liabilities
Contingent consideration		25,167
Derivative liabilities		234,011	84,855
ABS issued		8,346,051	5,410,073
Fair Value, Measurements, Recurring | Residential Loans
Assets
Residential loans		8,681,696	7,254,631
Fair Value, Measurements, Recurring | Level 1
Assets
Business purpose residential loans		0	0
Multifamily loans		0	0
Trading securities		0	0
Available-for-sale securities		0	0
Servicer advance investments		0	0
MSRs		0	0
Excess MSRs		0	0
Shared home appreciation options		0
Derivative assets		5,250	4,665
Pledged collateral		57,832	42,433
FHLBC stock		0	0
Guarantee asset		0	0
Liabilities
Contingent consideration		0
Derivative liabilities		4,192	13,215
ABS issued		0	0
Fair Value, Measurements, Recurring | Level 1 | Residential Loans
Assets
Residential loans		0	0
Fair Value, Measurements, Recurring | Level 2
Assets
Business purpose residential loans		0	0
Multifamily loans		0	0
Trading securities		0	0
Available-for-sale securities		0	0
Servicer advance investments		0	0
MSRs		0	0
Excess MSRs		0	0
Shared home appreciation options		0
Derivative assets		33,642	28,211
Pledged collateral		0	0
FHLBC stock		43,393	43,393
Guarantee asset		0	0
Liabilities
Contingent consideration		0
Derivative liabilities		228,150	70,908
ABS issued		0	0
Fair Value, Measurements, Recurring | Level 2 | Residential Loans
Assets
Residential loans		0	0
Fair Value, Measurements, Recurring | Level 3
Assets
Business purpose residential loans		336,035	141,258
Multifamily loans		3,791,622	2,144,598
Trading securities		1,013,785	1,118,612
Available-for-sale securities		271,641	333,882
Servicer advance investments		222,591	300,468
MSRs		39,837	60,281
Excess MSRs		32,937	27,312
Shared home appreciation options		11,372
Derivative assets		4,757	2,913
Pledged collateral		0	0
FHLBC stock		0	0
Guarantee asset		1,784	2,618
Liabilities
Contingent consideration		25,167
Derivative liabilities		1,669	732
ABS issued		8,346,051	5,410,073
Fair Value, Measurements, Recurring | Level 3 | Residential Loans
Assets
Residential loans		$ 8,681,696	$ 7,254,631

[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 September 30, 2019 and December 31, 2018, assets of consolidated VIEs totaled $9,596,537 and $6,331,191, respectively. At September 30, 2019 and December 31, 2018, liabilities of consolidated VIEs totaled $8,582,595 and $5,709,807, respectively. See Note 4 for further discussion.