Commitments and Contingencies - Additional Information (Details)			3 Months Ended				6 Months Ended
		Jun. 30, 2020 USD ($) lease	Jun. 30, 2020 USD ($) lease	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 partnership	Jun. 30, 2020 USD ($) repurchase_request loan lease	Jun. 30, 2019 USD ($) repurchase_request loan	Dec. 31, 2019 USD ($)	Mar. 01, 2019 USD ($)	May 31, 2018 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Lessee, number of leases | lease		7	7				7
Present value of remaining lease payments		$ 20,957,000	$ 20,957,000				$ 20,957,000
Operating lease expense							$ 2,000,000	$ 1,000,000
Number of new office leases | lease							3
Lease liability		$ 17,348,000	$ 17,348,000				$ 17,348,000		$ 13,443,000
Operating lease liability, statement of financial position [Extensible List]		us-gaap:AccruedLiabilitiesCurrentAndNoncurrent	us-gaap:AccruedLiabilitiesCurrentAndNoncurrent				us-gaap:AccruedLiabilitiesCurrentAndNoncurrent
Right-of-use asset		$ 15,561,000	$ 15,561,000				$ 15,561,000		11,866,000
Operating lease right-of-use asset, statement of financial position [Extensible List]		us-gaap:OtherAssets	us-gaap:OtherAssets				us-gaap:OtherAssets
Weighted average remaining lease term		8 years	8 years				8 years
Discount rate		5.00%	5.00%				5.00%
Derivative liabilities	[1]	$ 1,932,000	$ 1,932,000				$ 1,932,000		163,424,000
Number of partnerships, committed to fund | partnership						2
Commitment to fund partnership		94,000,000
Contingent consideration		14,953,000	14,953,000				14,953,000		28,484,000
Other income related to risk sharing agreement			1,181,000		$ 800,000		1,946,000	$ 1,446,000
Guarantee obligations		12,350,000	12,350,000				12,350,000		14,009,000
Guarantee obligations, credit reserve		5,000,000	5,000,000				5,000,000
Special purpose entities assets		47,000,000	47,000,000				47,000,000		48,000,000
Special purpose entities liabilities		12,000,000	12,000,000				12,000,000		14,000,000
Residential repurchase reserve		8,295,000	8,295,000				$ 8,295,000		4,268,000
Number of residential repurchase requests (in repurchase requests) | repurchase_request							5	7
Number of loans repurchased | loan							0	0
Residential loans repurchase provision (reversal)							$ (4,000,000)	$ (400,000)
Aggregate amount of loss contingency reserves									2,000,000
Damages sought							2,000,000
Loss contingency liability accrued		5,000,000	5,000,000				5,000,000
Minimum
Loss Contingencies [Line Items]
Reasonably possible losses estimated		0	0				0
Maximum
Loss Contingencies [Line Items]
Reasonably possible losses estimated		1,500,000	1,500,000				1,500,000
Residential Loans
Loss Contingencies [Line Items]
Loan principal		21,000,000	21,000,000				21,000,000		525,000,000
Balance of loans 90 days or more delinquent		1,000,000	1,000,000				1,000,000
Fair value of loans, in foreclosure		400,000	400,000				400,000
Financing Receivables, Equal to Greater than 90 Days Past Due | Residential Loans
Loss Contingencies [Line Items]
Balance of loans 90 days or more delinquent		3,000,000	3,000,000				3,000,000		$ 1,000,000
Other income
Loss Contingencies [Line Items]
Other income related to risk sharing agreement			1,000,000		1,000,000		2,000,000	1,000,000
Mortgage banking and investment activities
Loss Contingencies [Line Items]
Market valuation losses related to these investments			(200,000)		$ (100,000)		(700,000)	$ (100,000)
Guarantee Obligations
Loss Contingencies [Line Items]
Original unpaid balance of loans subject to risk sharing agreements												$ 3,190,000,000	$ 3,190,000,000
Potential future payments on loans		44,000,000	44,000,000				44,000,000
Loan principal		$ 1,300,000,000	$ 1,300,000,000				$ 1,300,000,000
Weighted average original FICO score		758	758				758
Weighted average original loan-to-value (LTV)		76.00%	76.00%				76.00%
Guarantee Obligations | Residential Loans
Loss Contingencies [Line Items]
Fair value of loans, in foreclosure		$ 0	$ 0				$ 0
Guarantee Obligations | Financing Receivables, Equal to Greater than 90 Days Past Due
Loss Contingencies [Line Items]
Balance of loans 90 days or more delinquent		17,000,000	17,000,000				17,000,000
Financial Guarantee
Loss Contingencies [Line Items]
Commitment to fund partnership		8,000,000
Guarantor obligations, current carrying value		100,000	100,000				100,000
Guarantor obligations, maximum exposure, undiscounted		135,000,000	135,000,000				135,000,000
Commitment To Fund Residential Bridge Loan
Loss Contingencies [Line Items]
Commitments to fund temporary advances		167,000,000	167,000,000				167,000,000
Derivative liabilities		2,000,000	2,000,000				2,000,000
Commitment To Fund Temporary Advances On Residential Bridge Loans
Loss Contingencies [Line Items]
Commitments to fund temporary advances		20,000,000	20,000,000				20,000,000
5 Arches
Loss Contingencies [Line Items]
Contingent consideration maximum amount											$ 29,000,000
Cash payment for contingent consideration liability				$ 11,000,000
Restricted stock awards				$ 3,000,000
Contingent consideration		15,000,000	15,000,000				15,000,000			$ 25,000,000
Shared home appreciation options
Loss Contingencies [Line Items]
Payments to acquire investments		47,000,000
Shared home appreciation options | Commitment To Fund Investment
Loss Contingencies [Line Items]
Commitments to fund temporary advances		$ 3,000,000	$ 3,000,000				$ 3,000,000

[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 Redwood Trust, Inc. or its affiliates. At June 30, 2020 and December 31, 2019, assets of consolidated VIEs totaled $7,984,618 and $11,931,869, respectively. At June 30, 2020 and December 31, 2019, liabilities of consolidated VIEs totaled $7,140,221 and $10,717,072, respectively. See Note 4 for further discussion.