v3.19.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2018
Mar. 12, 2019
Jun. 30, 2018
Document and Entity Information      
Entity Registrant Name GTX INC /DE/    
Entity Central Index Key 0001260990    
Document Type 10-K    
Document Period End Date Dec. 31, 2018    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Accelerated Filer    
Entity Public Float     $ 189,830,468
Entity Common Stock, Shares Outstanding   24,051,844  
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY