Long-Term Debt - Additional Information (Details)				1 Months Ended					12 Months Ended
		Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2018 USD ($) $ / shares	Aug. 31, 2017 USD ($) $ / shares	Jan. 31, 2016	Nov. 30, 2014 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2016 USD ($)	Nov. 30, 2019 USD ($)	Dec. 31, 2013 USD ($)
Debt Instrument [Line Items]
FHLB transition period							5 years
Committed line of credit with financial institutions, outstanding		$ 0	$ 0						$ 0
Federal home loan bank stock		43,393,000	43,393,000						43,393,000
Accrued interest payable		6,000,000	4,000,000						6,000,000
Convertible notes			201,000,000								$ 201,000,000
Notional amount		13,589,356,000	5,911,385,000						13,589,356,000
Accrued interest payable	[1]	60,655,000	42,528,000						60,655,000
Convertible notes | Exchangeable Senior Notes Due 2025
Debt Instrument [Line Items]
Debt instrument interest rate				5.75%
Unamortized deferred issuance costs		6,000,000							6,000,000
Convertible notes		$ 201,000,000		$ 201,000,000					$ 201,000,000
Net proceeds from issuance of convertible debt				$ 195,000,000
Interest expense yield				6.30%
Convertible debt, conversion ratio		0.0551967
Convertible senior notes conversion per share (in dollars per share) | $ / shares		$ 18.12							$ 18.12
Accrued interest payable		$ 3,000,000							$ 3,000,000
Convertible notes | Senior Notes Due 2024
Debt Instrument [Line Items]
Debt instrument interest rate					5.625%
Unamortized deferred issuance costs		4,000,000							4,000,000
Convertible notes		200,000,000			$ 200,000,000				200,000,000
Net proceeds from issuance of convertible debt					$ 194,000,000
Interest expense yield					6.20%
Convertible debt, conversion ratio					0.0547645
Convertible senior notes conversion per share (in dollars per share) | $ / shares					$ 18.26
Accrued interest payable		5,000,000							5,000,000
Percent of par at issuance					99.50%
Debt discount		1,000,000							1,000,000
Convertible notes | Senior Notes Due 2023
Debt Instrument [Line Items]
Debt instrument interest rate						4.75%
Unamortized deferred issuance costs		5,000,000							5,000,000
Convertible notes		245,000,000				$ 245,000,000			245,000,000
Net proceeds from issuance of convertible debt						$ 238,000,000
Interest expense yield						5.30%
Convertible debt, conversion ratio						0.0543346
Convertible senior notes conversion per share (in dollars per share) | $ / shares						$ 18.40
Accrued interest payable		4,000,000							4,000,000
Convertible notes | Exchangeable senior notes due 2019
Debt Instrument [Line Items]
Debt instrument interest rate								5.625%
Convertible notes								$ 205,000,000
Net proceeds from issuance of convertible debt								$ 198,000,000
Interest expense yield								6.30%
Convertible debt, conversion ratio								0.0465404
Convertible senior notes conversion per share (in dollars per share) | $ / shares								$ 21.49
Repurchased debt instrument, face amount										$ 4,000,000
Deferred debt issuance costs			1,000,000
Convertible notes | Exchangeable senior notes due 2019 | Gain (Loss) on Investments
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt										$ 300,000
Trust Preferred Securities
Debt Instrument [Line Items]
Long-term debt, net		100,000,000							$ 100,000,000
Interest expense yield on trust preferred securities and subordinated notes									6.90%
Subordinated Notes
Debt Instrument [Line Items]
Long-term debt, net		40,000,000							$ 40,000,000
Trust Preferred Securities and Subordinated Notes
Debt Instrument [Line Items]
Accrued interest payable		1,000,000	1,000,000						$ 1,000,000
Trust Preferred Securities and Subordinated Notes | Interest rate agreements
Debt Instrument [Line Items]
Notional amount												$ 140,000,000
Trust Preferred Securities and Subordinated Notes | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate									2.25%
Affiliated Entity | Long Term Non Market To market Recourse Debt Financing
Debt Instrument [Line Items]
Debt instrument interest rate				4.21%
Long-term debt, gross		185,000,000							$ 185,000,000
Unamortized deferred issuance costs		1,000,000							1,000,000
Long-term debt, net		184,000,000							184,000,000
Pledged assets real estate pledged as collateral, at fair value		250,000,000							250,000,000
Affiliated Entity | Sequoia Choice | Long Term Non Market To market Recourse Debt Financing
Debt Instrument [Line Items]
Pledged assets real estate pledged as collateral, at fair value		125,000,000							$ 125,000,000
FHLB Chicago
Debt Instrument [Line Items]
Interest rate margin reset period									91 days
FHLB Chicago | Subsidiaries
Debt Instrument [Line Items]
Additional borrowings from FHLB									$ 0
FHLB Chicago | FHLB Subsidiary
Debt Instrument [Line Items]
Maximum borrowing capacity		2,000,000,000.00							2,000,000,000.00
Committed line of credit with financial institutions, outstanding		2,000,000,000.00							2,000,000,000.00
Outstanding FHLB advances		$ 2,000,000,000.00	$ 2,000,000,000.00						$ 2,000,000,000.00
Weighted average interest rate		1.88%	2.52%						1.88%
Weighted average maturity (in years)		6 years	7 years
Long-term debt, net		$ 1,999,999,000							$ 1,999,999,000
FHLB Chicago | Redwood | Held-for sale residential loans | Residential Real Estate
Debt Instrument [Line Items]
Residential mortgage loans securing FHLB advances		2,100,000,000							2,100,000,000
FHLB Chicago | Redwood | Held-for sale residential loans | Equity Securities
Debt Instrument [Line Items]
Residential mortgage loans securing FHLB advances		39,000,000							39,000,000
FHLB Chicago | Redwood | Held-for sale residential loans | Restricted cash
Debt Instrument [Line Items]
Residential mortgage loans securing FHLB advances		59,000,000							59,000,000
FHLB Chicago | Redwood | Single-family rental loans held-for-investment | Residential Real Estate
Debt Instrument [Line Items]
Residential mortgage loans securing FHLB advances		$ 211,000,000							$ 211,000,000

[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 December 31, 2019 and December 31, 2018, assets of consolidated VIEs totaled $11,931,869 and $6,331,191, respectively. At December 31, 2019 and December 31, 2018, liabilities of consolidated VIEs totaled $10,717,072 and $5,709,807, respectively. See Note 4 for further discussion.