Document and Entity Information - $ / shares	9 Months Ended
	Sep. 30, 2021	Oct. 25, 2021
Cover [Abstract]
Entity Central Index Key	0001597264
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-37359
Entity Registrant Name	BLUEPRINT MEDICINES CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-3632015
Entity Address, Address Line One	45 Sidney Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	374-7580
Title of 12(b) Security	Common stock, par value $0.001 per share
Trading Symbol	BPMC
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Listing, Par Value Per Share	$ 0.001
Entity Common Stock, Shares Outstanding		58,838,034
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false