Short-Term Debt - Outstanding Balances of Short-Term Debt by Type of Collateral Securing Debt (Details)		12 Months Ended
		Dec. 31, 2020 USD ($) facility	Dec. 31, 2019 USD ($) facility
Short-term Debt [Line Items]
Outstanding Balance	[1]	$ 522,609,000	$ 2,329,145,000
Line of Credit
Short-term Debt [Line Items]
Number of Facilities | facility		9	22
Outstanding Balance		$ 314,234,000	$ 2,176,591,000
Line of Credit | Residential loan warehouse
Short-term Debt [Line Items]
Number of Facilities | facility		4	4
Outstanding Balance		$ 137,269,000	$ 185,894,000
Limit		$ 1,300,000,000	$ 1,425,000,000
Weighted Average Interest Rate		2.45%	3.23%
Weighted Average Days Until Maturity		268 days	69 days
Line of Credit | Business purpose loans
Short-term Debt [Line Items]
Number of Facilities | facility		2	8
Outstanding Balance		$ 99,190,000	$ 814,118,000
Limit		$ 500,000,000	$ 1,475,000,000
Weighted Average Interest Rate		3.37%	4.11%
Weighted Average Days Until Maturity		521 days	489 days
Line of Credit | Real estate securities repo
Short-term Debt [Line Items]
Number of Facilities | facility		3	10
Outstanding Balance		$ 77,775,000	$ 1,176,579,000
Limit		$ 0	$ 0
Weighted Average Interest Rate		2.24%	2.94%
Weighted Average Days Until Maturity		36 days	23 days
Servicer advance financing
Short-term Debt [Line Items]
Number of Facilities | facility		1	1
Outstanding Balance		$ 208,375,000	$ 152,554,000
Limit		$ 335,000,000	$ 400,000,000
Weighted Average Interest Rate		1.95%	3.56%
Weighted Average Days Until Maturity		334 days	335 days

[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.