v3.10.0.1
Document and Entity Information - $ / shares
9 Months Ended
Sep. 30, 2018
Oct. 26, 2018
Document and Entity Information [Abstract]    
Entity Registrant Name Blueprint Medicines Corp  
Entity Central Index Key 0001597264  
Document Type 10-Q  
Document Period End Date Sep. 30, 2018  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Listing, Par Value Per Share $ 0.001  
Entity Common Stock, Shares Outstanding   43,950,375
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3