Commitments and Contingencies - Additional Information (Details)			3 Months Ended			12 Months Ended		48 Months Ended
		Mar. 31, 2020 USD ($) lease	Mar. 31, 2020 USD ($) loan repurchase_request certificate lease	Mar. 31, 2019 USD ($) loan repurchase_request	Dec. 31, 2018 partnership	Dec. 31, 2007 certificate	Dec. 31, 2004 certificate	Dec. 31, 2007 certificate	Dec. 31, 2019 USD ($)	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
Present value of remaining lease payments		$ 21,873,000	$ 21,873,000
Operating lease expense			$ 1,000,000	$ 1,000,000
Lessee, Operating Lease, Number of New Leases | lease			3
Lease liability		18,072,000	$ 18,072,000						$ 13,443,000
Right-of-use asset		$ 16,375,000	$ 16,375,000						11,866,000
Weighted average remaining lease term		8 years	8 years
Discount rate		4.90%	4.90%
Derivative liabilities	[1]	$ 114,614,000	$ 114,614,000						163,424,000
Number of partnerships, committed to fund | partnership					2
Commitment to fund partnership		90,000,000
Contingent consideration		14,819,000	14,819,000						28,484,000
Other income related to risk sharing agreement			765,000	$ 646,000
Guarantee obligations		13,395,000	13,395,000						14,009,000
Guarantee obligations, credit reserve		5,000,000	5,000,000
Special purpose entities assets		47,000,000	47,000,000						48,000,000
Special purpose entities liabilities		13,000,000	13,000,000						14,000,000
Residential repurchase reserve		4,460,000	$ 4,460,000						4,268,000
Number of residential repurchase requests (in repurchase requests) | repurchase_request			3	4
Number of loans repurchased | loan			0	0
Residential loans repurchase provision (reversal)			$ (200,000)	$ (100,000)
Damages sought			2,000,000
Aggregate amount of loss contingency reserves									2,000,000
Minimum
Loss Contingencies [Line Items]
Reasonably possible losses estimated		0	0
Maximum
Loss Contingencies [Line Items]
Reasonably possible losses estimated		10,000,000	$ 10,000,000
Morgan Stanley And Company
Loss Contingencies [Line Items]
Number of mortgage pass-through certificates issued (in certificates) | certificate			28
Sequoia Residential Funding
Loss Contingencies [Line Items]
Number of mortgage pass-through certificates issued (in certificates) | certificate						2	2	4
Residential Loans
Loss Contingencies [Line Items]
Loan principal		2,370,000,000	$ 2,370,000,000						$ 525,000,000
Loans held-for-investment, in foreclosure		400,000	400,000
Other income
Loss Contingencies [Line Items]
Other income related to risk sharing agreement			1,000,000	1,000,000
Mortgage banking and investment activities
Loss Contingencies [Line Items]
Market valuation losses related to these investments			(500,000)	$ (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
Loan principal		$ 1,470,000,000	$ 1,470,000,000
Weighted average original FICO score		759	759
Weighted average original loan-to-value (LTV)		76.00%	76.00%
Guarantee Obligations | Residential Loans
Loss Contingencies [Line Items]
Loans held-for-investment, in foreclosure		$ 1,000,000	$ 1,000,000
Guarantee Obligations | Financing Receivables, Equal to Greater than 90 Days Past Due
Loss Contingencies [Line Items]
Balance of loans 90 days or more delinquent		6,000,000	6,000,000
Financial Guarantee
Loss Contingencies [Line Items]
Commitment to fund partnership		24,000,000
Guarantor obligations, current carrying value		100,000	100,000
Guarantor obligations, maximum exposure, undiscounted		135,000,000	135,000,000
Commitment To Fund Residential Bridge Loan
Loss Contingencies [Line Items]
Commitments to fund temporary advances		223,000,000	223,000,000
Derivative liabilities		4,000,000	4,000,000
Commitment To Fund Temporary Advances On Residential Bridge Loans
Loss Contingencies [Line Items]
Commitments to fund temporary advances		44,000,000	44,000,000
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							$ 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

[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 March 31, 2020 and December 31, 2019, assets of consolidated VIEs totaled $7,470,706 and $11,931,869, respectively. At March 31, 2020 and December 31, 2019, liabilities of consolidated VIEs totaled $6,759,260 and $10,717,072, respectively. See Note 4 for further discussion.