Document and Entity Information - shares
6 Months Ended
Jun. 30, 2018
Aug. 09, 2018
Document and Entity Information    
Entity Registrant Name GTX INC /DE/  
Entity Central Index Key 0001260990  
Document Type 10-Q  
Document Period End Date Jun. 30, 2018  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Smaller Reporting Company  
Entity Common Stock, Shares Outstanding   24,045,844
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q2