| Document and Entity Information | May 17, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | ZIOPHARM ONCOLOGY INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001107421 |
| Current Fiscal Year End Date | --12-31 |
| Document Type | 8-K |
| Document Period End Date | May 17, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-33038 |
| Entity Tax Identification Number | 84-1475642 |
| Entity Address, Address Line One | One First Avenue |
| Entity Address, Address Line Two | Parris Building 34 |
| Entity Address, Address Line Three | Navy Yard Plaza |
| Entity Address, City or Town | Boston |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02129 |
| City Area Code | (617) |
| Local Phone Number | 259-1970 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.001 per share |
| Trading Symbol | ZIOP |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
