| Cover Page | Mar. 17, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 17, 2021 |
| Entity Registrant Name | CTI BIOPHARMA CORP. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 000-28386 |
| Entity Tax Identification Number | 91-1533912 |
| Entity Address, Address Line One | 3101 Western Avenue |
| Entity Address, Address Line Two | Suite 800 |
| Entity Address, City or Town | Seattle |
| Entity Address, State or Province | WA |
| Entity Address, Postal Zip Code | 98121 |
| City Area Code | 206 |
| Local Phone Number | 282-7100 |
| 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 $0.001 |
| Trading Symbol | CTIC |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000891293 |
| Amendment Flag | false |
