Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 26, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-13759
Entity Registrant Name	REDWOOD TRUST, INC.
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	68-0329422
Entity Address, Address Line One	One Belvedere Place, Suite 300
Entity Address, City or Town	Mill Valley,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94941
City Area Code	415
Local Phone Number	389-7373
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	RWT
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,600,621,984
Entity Common Stock, Shares Outstanding		114,353,805
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement to be filed with the Securities and Exchange Commission under Regulation 14A within 120 days after the end of registrant’s fiscal year covered by this Annual Report are incorporated by reference into Part III.
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0000930236
Current Fiscal Year End Date	--12-31