Document and Entity Information - shares
6 Months Ended
Jun. 30, 2019
Jul. 24, 2019
Document and Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Entity Registrant Name ZIOPHARM ONCOLOGY INC  
Entity Central Index Key 0001107421  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Trading Symbol ZIOP  
Entity Emerging Growth Company false  
Entity Small Business true  
Entity Common Stock, Shares Outstanding   162,552,963
Entity Interactive Data Current Yes  
Title of 12(b) Security Common Stock  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Shell Company false  
Entity Address, State or Province MA