v3.19.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2018
Mar. 15, 2019
Jun. 30, 2018
Document and Entity Information      
Entity Registrant Name STEMLINE THERAPEUTICS INC    
Entity Central Index Key 0001264587    
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 Small Business true    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 448,641,317
Entity Common Stock, Shares Outstanding   43,569,081  
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY