Commitments and Contingencies - Additional Information (Details) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
		May 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 partnership	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) lease loan repurchase_request	Dec. 31, 2019 USD ($) repurchase_request loan	Dec. 31, 2018 USD ($) loan	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						8
Present value of remaining lease payments						$ 19,925
Operating lease expense						4,000	$ 3,000	$ 2,000
Unamortized leasehold improvements						3,000
Leasehold amortization expense						$ 500	400	200
Number of new leases | lease						4
Lease liability						$ 16,687	$ 13,443
Operating Lease, Liability, Statement of Financial Position [Extensible List]						us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent
Operating lease right-of-use assets						$ 15,012	$ 11,866
Weighted average remaining lease term						7 years
Discount rate						4.90%
Derivative liabilities	[1]					$ 16,072	163,424
Number of partnerships, committed to fund | partnership				2
Contingent consideration						0	28,484
Risk share income						4,367	3,522	$ 3,613
Principal amount outstanding on loans securitized						172,748	524,928
Guarantee obligations						10,039	14,009
Guarantee obligation, credit reserve						5,000
SPE, assets						46,000	48,000
SPE, liabilities						10,000	14,000
Residential loan and MSR repurchase reserve						$ 8,631	$ 4,268
Residential loans repurchase requests | repurchase_request						10	15
Residential loans, number of loans repurchased | loan						1	0	2
Residential loans repurchase provision (reversal)						$ 4,000	$ 100	$ 700
Residential loans repurchased during period						100	0	0
Aggregate amount of loss contingency reserves					$ 2,000
Damages sought		$ 2,000
Residential Loan Seller Demands
Loss Contingencies [Line Items]
Expenses from litigation recorded					10,000
Aggregate amount of accrual					$ 2,500
Residential Loans
Loss Contingencies [Line Items]
Principal amount outstanding on loans securitized						172,748	525,069
Financing Receivables, Equal to Greater than 90 Days Past Due | Residential Loans
Loss Contingencies [Line Items]
Loans past due						1,882	747
Other Income
Loss Contingencies [Line Items]
Risk share income						4,000	4,000	4,000
Mortgage Banking And Investment Activities
Loss Contingencies [Line Items]
Market valuation changes in fair value of guarantee asset						1,000	$ 200	$ 400
Guarantee Obligations
Loss Contingencies [Line Items]
Original principal balance of loans sold subject to risk sharing agreement											$ 3,190,000	$ 3,190,000
Potential future payments on risk sharing agreements						44,000
Principal amount outstanding on loans securitized						$ 938,000
FICO credit score						757
Loan to value ratio						75.00%
Guarantee Obligations | Residential Loans
Loss Contingencies [Line Items]
Loans held as assets amount in foreclosure						$ 200
Guarantee Obligations | Financing Receivables, Equal to Greater than 90 Days Past Due
Loss Contingencies [Line Items]
Loans past due						39,000
Commitment To Fund Residential Bridge Loan
Loss Contingencies [Line Items]
Commitments to fund temporary advances						216,000
Derivative liabilities						2,000
Commitment To Fund Temporary Advances On Residential Bridge Loans
Loss Contingencies [Line Items]
Commitments to fund temporary advances						8,000
Shared home appreciation options
Loss Contingencies [Line Items]
Payments to acquire investments						47,000
5 Arches, LLC
Loss Contingencies [Line Items]
Contingent consideration maximum amount									$ 27,000	$ 29,000
Cash payment for contingent consideration			$ 11,000
Restricted stock awards			$ 3,000
Contingent consideration						$ 15,000			$ 24,621

[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, 2020 and December 31, 2019, assets of consolidated VIEs totaled $8,141,069 and $11,931,869, respectively. At December 31, 2020 and December 31, 2019, liabilities of consolidated VIEs totaled $7,148,414 and $10,717,072, respectively. See Note 4 for further discussion.