Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Assets
Real estate securities		$ 144,162	$ 860,540
MSRs		242,059	151,582
Derivative assets	[1]	14,709	35,701
Pledged collateral		8,172	32,945
Liabilities
Contingent consideration		0	28,484
Derivative liabilities	[1]	1,612	163,424
ABS issued		6,969,376	10,515,475
Fair Value, Measurements, Recurring
Assets
Business purpose residential loans		3,956,101	3,506,743
Multifamily loans		491,415	4,408,524
Real estate securities		351,335	1,099,874
Servicer advance investments		258,621	169,204
MSRs		14,878	42,224
Excess MSRs		35,070	31,814
Shared home appreciation options		41,758	45,085
Derivative assets		14,709	35,701
Pledged collateral		8,172	32,945
FHLBC stock		5,000	43,393
Guarantee asset		579	1,686
Liabilities
Contingent consideration			28,484
Derivative liabilities		1,612	163,424
ABS issued		6,969,376	10,515,475
Fair Value, Measurements, Recurring | Residential Loans
Assets
Residential loans		4,494,899	7,714,745
Fair Value, Measurements, Recurring | Level 1
Assets
Business purpose residential loans		0	0
Multifamily loans		0	0
Real estate securities		0	0
Servicer advance investments		0	0
MSRs		0	0
Excess MSRs		0	0
Shared home appreciation options		0	0
Derivative assets		464	6,531
Pledged collateral		8,172	32,945
FHLBC stock		0	0
Guarantee asset		0	0
Liabilities
Contingent consideration			0
Derivative liabilities		263	13,368
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
Real estate securities		0	0
Servicer advance investments		0	0
MSRs		0	0
Excess MSRs		0	0
Shared home appreciation options		0	0
Derivative assets		3,472	19,020
Pledged collateral		0	0
FHLBC stock		5,000	43,393
Guarantee asset		0	0
Liabilities
Contingent consideration			0
Derivative liabilities		15	148,766
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		3,956,101	3,506,743
Multifamily loans		491,415	4,408,524
Real estate securities		351,335	1,099,874
Servicer advance investments		258,621	169,204
MSRs		14,878	42,224
Excess MSRs		35,070	31,814
Shared home appreciation options		41,758	45,085
Derivative assets		10,773	10,150
Pledged collateral		0	0
FHLBC stock		0	0
Guarantee asset		579	1,686
Liabilities
Contingent consideration			28,484
Derivative liabilities		1,334	1,290
ABS issued		6,969,376	10,515,475
Fair Value, Measurements, Recurring | Level 3 | Residential Loans
Assets
Residential loans		$ 4,494,899	$ 7,714,745

[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, 2020 and December 31, 2019, assets of consolidated VIEs totaled $8,197,095 and $11,931,869, respectively. At September 30, 2020 and December 31, 2019, liabilities of consolidated VIEs totaled $7,238,047 and $10,717,072, respectively. See Note 4 for further discussion.