| Cover | Feb. 18, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 18, 2021 |
| Entity File Number | 001-13759 |
| Entity Registrant Name | REDWOOD TRUST, INC. |
| Entity Central Index Key | 0000930236 |
| Entity Tax Identification Number | 68-0329422 |
| Entity Incorporation, State or Country Code | MD |
| Entity Address, Address Line One | One Belvedere Place |
| Entity Address, Address Line Two | 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.01 per share |
| Trading Symbol | RWT |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
