Document and Entity Information
6 Months Ended
Jun. 30, 2014
Jul. 31, 2014
Document and Entity Information    
Entity Registrant Name Karyopharm Therapeutics Inc.  
Entity Central Index Key 0001503802  
Document Type 10-Q  
Document Period End Date Jun. 30, 2014  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   32,670,103
Document Fiscal Year Focus 2014  
Document Fiscal Period Focus Q2